[flutter_releases] Flutter beta 2.9.0-0.1.pre Framework Cherrypicks (#95275)

* 'add branch flutter-2.8-candidate.10 to enabled_branches in .ci.yaml'

* 'Update Engine revision to 234aca678a2fb70ff2659870186f97c32f8894f4 for beta release 2.9.0-0.1.pre'

* Remove redundant entry in .ci.yaml file.
diff --git a/bin/internal/engine.version b/bin/internal/engine.version
index 1364722..6bb6e80 100644
--- a/bin/internal/engine.version
+++ b/bin/internal/engine.version
@@ -1 +1 @@
-66a281107bcfd0283f469694980924e8f32b7a32
+234aca678a2fb70ff2659870186f97c32f8894f4