[flutter_releases] Flutter beta 2.7.0-3.1.pre Framework Cherrypicks (#92605)

* [ci.yaml] Explicitly use scheduler==luci (#92218)

* 'Update Engine revision to a75e3b80f9c1ffb30bbe736c5a42e4a815a79197 for beta release 2.7.0-3.1.pre'

* [ci.yaml] Disable plugins_test on release branches (#92442)

Co-authored-by: Casey Hillers <chillers@google.com>
diff --git a/.ci.yaml b/.ci.yaml
index fc0ffa3..2a0b104 100755
--- a/.ci.yaml
+++ b/.ci.yaml
@@ -354,6 +354,9 @@
   - name: Linux flutter_plugins
     recipe: flutter/flutter_drone
     timeout: 60
+    enabled_branches:
+      - main
+      - master
     properties:
       shard: flutter_plugins
       subshard: analyze
@@ -2331,6 +2334,7 @@
         ["framework","hostonly","shard"]
       validation: verify_binaries_codesigned
       validation_name: Verify binaries codesigned
+    scheduler: luci
 
   - name: Mac web_tool_tests
     recipe: flutter/flutter_drone
diff --git a/bin/internal/engine.version b/bin/internal/engine.version
index fff707a..47eae8a 100644
--- a/bin/internal/engine.version
+++ b/bin/internal/engine.version
@@ -1 +1 @@
-bbba2b2437d739a455ecafb66a22a46d31b233ed
+a75e3b80f9c1ffb30bbe736c5a42e4a815a79197