Update testing_ref for beta branch.

This is used to ensure post-submit builds work correctly.

Change-Id: I56536ddc3ace7fe1d0c56aebba312043329b9752
diff --git a/config/generated/flutter/luci/luci-milo.cfg b/config/generated/flutter/luci/luci-milo.cfg
index 75974d8..19b1566 100644
--- a/config/generated/flutter/luci/luci-milo.cfg
+++ b/config/generated/flutter/luci/luci-milo.cfg
@@ -1779,7 +1779,7 @@
   id: "beta_flutter"
   name: "beta_flutter"
   repo_url: "https://flutter.googlesource.com/mirrors/flutter"
-  refs: "regexp:refs/heads/flutter-3\\.1-candidate\\.*"
+  refs: "regexp:refs/heads/flutter-2\\.13-candidate\\.5"
   manifest_name: "REVISION"
   builders {
     name: "buildbucket/luci.flutter.prod/Linux beta analyze"
@@ -9347,7 +9347,7 @@
   id: "beta_engine"
   name: "beta_engine"
   repo_url: "https://flutter.googlesource.com/mirrors/engine"
-  refs: "regexp:refs/heads/flutter-3\\.1-candidate\\.*"
+  refs: "regexp:refs/heads/flutter-2\\.13-candidate\\.5"
   manifest_name: "REVISION"
   builders {
     name: "buildbucket/luci.flutter.prod/Linux beta Android AOT Engine"
diff --git a/config/generated/flutter/luci/luci-scheduler.cfg b/config/generated/flutter/luci/luci-scheduler.cfg
index 574c8ba..20bd3af 100644
--- a/config/generated/flutter/luci/luci-scheduler.cfg
+++ b/config/generated/flutter/luci/luci-scheduler.cfg
@@ -12520,7 +12520,7 @@
   acl_sets: "prod"
   gitiles {
     repo: "https://flutter.googlesource.com/mirrors/engine"
-    refs: "regexp:refs/heads/flutter-3\\.1-candidate\\.*"
+    refs: "regexp:refs/heads/flutter-2\\.13-candidate\\.5"
   }
 }
 trigger {
@@ -12776,7 +12776,7 @@
   triggers: "Windows_android beta windows_chrome_dev_mode"
   gitiles {
     repo: "https://flutter.googlesource.com/mirrors/flutter"
-    refs: "regexp:refs/heads/flutter-3\\.1-candidate\\.*"
+    refs: "regexp:refs/heads/flutter-2\\.13-candidate\\.5"
   }
 }
 trigger {
diff --git a/config/lib/release_branches/branches.json b/config/lib/release_branches/branches.json
index a335a39..8b0d79a 100644
--- a/config/lib/release_branches/branches.json
+++ b/config/lib/release_branches/branches.json
@@ -6,7 +6,7 @@
         "version": "2_13_0"
     },
     "beta": {
-        "testing_ref": "refs/heads/flutter-3\\.1-candidate\\.*",
+        "testing_ref": "refs/heads/flutter-2\\.13-candidate\\.5",
         "release_ref": "refs/heads/beta",
         "recipes_ref": "refs/heads/main",
         "version": "2_14_0"