Remove `schedule_during_release_override`, which is no longer used. (#4758)

Closes https://github.com/flutter/flutter/issues/168913.

Wait until https://github.com/flutter/flutter/pull/169912 is submitted to submit this.
diff --git a/app_dart/lib/src/model/proto/internal/scheduler.pb.dart b/app_dart/lib/src/model/proto/internal/scheduler.pb.dart
index b97c0e8..01925a3 100644
--- a/app_dart/lib/src/model/proto/internal/scheduler.pb.dart
+++ b/app_dart/lib/src/model/proto/internal/scheduler.pb.dart
@@ -198,7 +198,6 @@
     $core.Map<$core.String, $core.String>? dimensions,
     $core.Iterable<$core.String>? droneDimensions,
     $core.bool? backfill,
-    $core.bool? scheduleDuringReleaseOverride,
   }) {
     final $result = create();
     if (name != null) {
@@ -250,9 +249,6 @@
     if (backfill != null) {
       $result.backfill = backfill;
     }
-    if (scheduleDuringReleaseOverride != null) {
-      $result.scheduleDuringReleaseOverride = scheduleDuringReleaseOverride;
-    }
     return $result;
   }
   Target._() : super();
@@ -305,7 +301,6 @@
     ..pPS(17, _omitFieldNames ? '' : 'droneDimensions')
     ..a<$core.bool>(19, _omitFieldNames ? '' : 'backfill', $pb.PbFieldType.OB,
         defaultOrMaker: true)
-    ..aOB(20, _omitFieldNames ? '' : 'scheduleDuringReleaseOverride')
     ..hasRequiredFields = false;
 
   @$core.Deprecated('Using this can add significant overhead to your binary. '
@@ -491,23 +486,6 @@
   $core.bool hasBackfill() => $_has(15);
   @$pb.TagNumber(19)
   void clearBackfill() => clearField(19);
-
-  ///  Whether the target should be scheduld by the release_builder process.
-  ///
-  ///  This plays a similar role to "scheduler: release", except that backfill,
-  ///  presubmit, postsubmit, and other attributes are still respected in other
-  ///  parts of Cocoon.
-  @$pb.TagNumber(20)
-  $core.bool get scheduleDuringReleaseOverride => $_getBF(16);
-  @$pb.TagNumber(20)
-  set scheduleDuringReleaseOverride($core.bool v) {
-    $_setBool(16, v);
-  }
-
-  @$pb.TagNumber(20)
-  $core.bool hasScheduleDuringReleaseOverride() => $_has(16);
-  @$pb.TagNumber(20)
-  void clearScheduleDuringReleaseOverride() => clearField(20);
 }
 
 const _omitFieldNames = $core.bool.fromEnvironment('protobuf.omit_field_names');
diff --git a/app_dart/lib/src/model/proto/internal/scheduler.pbjson.dart b/app_dart/lib/src/model/proto/internal/scheduler.pbjson.dart
index 6173013..bd55d6c 100644
--- a/app_dart/lib/src/model/proto/internal/scheduler.pbjson.dart
+++ b/app_dart/lib/src/model/proto/internal/scheduler.pbjson.dart
@@ -199,14 +199,6 @@
     },
     {'1': 'drone_dimensions', '3': 17, '4': 3, '5': 9, '10': 'droneDimensions'},
     {'1': 'backfill', '3': 19, '4': 1, '5': 8, '7': 'true', '10': 'backfill'},
-    {
-      '1': 'schedule_during_release_override',
-      '3': 20,
-      '4': 1,
-      '5': 8,
-      '7': 'false',
-      '10': 'scheduleDuringReleaseOverride'
-    },
   ],
   '3': [
     Target_PropertiesEntry$json,
@@ -217,6 +209,7 @@
     {'1': 2, '2': 3},
     {'1': 14, '2': 15},
     {'1': 18, '2': 19},
+    {'1': 20, '2': 21},
   ],
 };
 
@@ -264,9 +257,8 @@
     'FyZ2V0LlBvc3RzdWJtaXRQcm9wZXJ0aWVzRW50cnlSFHBvc3RzdWJtaXRQcm9wZXJ0aWVzEkEK'
     'CmRpbWVuc2lvbnMYECADKAsyIS5zY2hlZHVsZXIuVGFyZ2V0LkRpbWVuc2lvbnNFbnRyeVIKZG'
     'ltZW5zaW9ucxIpChBkcm9uZV9kaW1lbnNpb25zGBEgAygJUg9kcm9uZURpbWVuc2lvbnMSIAoI'
-    'YmFja2ZpbGwYEyABKAg6BHRydWVSCGJhY2tmaWxsEk4KIHNjaGVkdWxlX2R1cmluZ19yZWxlYX'
-    'NlX292ZXJyaWRlGBQgASgIOgVmYWxzZVIdc2NoZWR1bGVEdXJpbmdSZWxlYXNlT3ZlcnJpZGUa'
-    'PQoPUHJvcGVydGllc0VudHJ5EhAKA2tleRgBIAEoCVIDa2V5EhQKBXZhbHVlGAIgASgJUgV2YW'
-    'x1ZToCOAEaRwoZUG9zdHN1Ym1pdFByb3BlcnRpZXNFbnRyeRIQCgNrZXkYASABKAlSA2tleRIU'
-    'CgV2YWx1ZRgCIAEoCVIFdmFsdWU6AjgBGj0KD0RpbWVuc2lvbnNFbnRyeRIQCgNrZXkYASABKA'
-    'lSA2tleRIUCgV2YWx1ZRgCIAEoCVIFdmFsdWU6AjgBSgQIAhADSgQIDhAPSgQIEhAT');
+    'YmFja2ZpbGwYEyABKAg6BHRydWVSCGJhY2tmaWxsGj0KD1Byb3BlcnRpZXNFbnRyeRIQCgNrZX'
+    'kYASABKAlSA2tleRIUCgV2YWx1ZRgCIAEoCVIFdmFsdWU6AjgBGkcKGVBvc3RzdWJtaXRQcm9w'
+    'ZXJ0aWVzRW50cnkSEAoDa2V5GAEgASgJUgNrZXkSFAoFdmFsdWUYAiABKAlSBXZhbHVlOgI4AR'
+    'o9Cg9EaW1lbnNpb25zRW50cnkSEAoDa2V5GAEgASgJUgNrZXkSFAoFdmFsdWUYAiABKAlSBXZh'
+    'bHVlOgI4AUoECAIQA0oECA4QD0oECBIQE0oECBQQFQ==');
diff --git a/app_dart/lib/src/model/proto/internal/scheduler.proto b/app_dart/lib/src/model/proto/internal/scheduler.proto
index e98e8d7..58bf274 100644
--- a/app_dart/lib/src/model/proto/internal/scheduler.proto
+++ b/app_dart/lib/src/model/proto/internal/scheduler.proto
@@ -69,12 +69,7 @@
     reserved 18; // run_if_not
     // Whether the target should be considered for backfill.
     optional bool backfill = 19 [default = true];
-    // Whether the target should be scheduld by the release_builder process.
-    //
-    // This plays a similar role to "scheduler: release", except that backfill,
-    // presubmit, postsubmit, and other attributes are still respected in other
-    // parts of Cocoon.
-    optional bool schedule_during_release_override = 20 [default = false];
+    reserved 20; // schedule_during_release_override
 }
 
 // Schedulers supported in SchedulerConfig.