Manually roll Flutter Engine from cbb9d0b06 to cef721963 (#112895)

https://github.com/flutter/engine/compare/37d8342ccac159892d93008f64c9a3ac0ed2f9e1...cef721963336c56e88127d82db6400ff1d247b26

* Revert "[Windows] Move to Visual Studio 2019" (https://github.com/flutter/engine/pull/36606)

Issue: https://github.com/flutter/flutter/issues/112894
https://dart.googlesource.com/external/github.com/flutter/flutter/+/76dd29f6a819ad72393cb6670888ed3d2191c928
diff --git a/DEPS b/DEPS
index f60fe44..7a0a1ae 100644
--- a/DEPS
+++ b/DEPS
@@ -116,7 +116,7 @@
 
   'engine/src/third_party/dart': Var('dart_git') + '/sdk' + '@' + 'ce7c036db217b43014a05dcbdc377e3bcb7743ae',
 
-  'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + '2fdfa29e081bb368bf11b6177e4e9bb7c8ad4d34',
+  'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + '76dd29f6a819ad72393cb6670888ed3d2191c928',
 
    # Fuchsia compatibility
    #
diff --git a/commits.json b/commits.json
index 16cb916..9b8b938 100644
--- a/commits.json
+++ b/commits.json
@@ -1,5 +1,5 @@
 {
   "engine/src/flutter":"cef721963336c56e88127d82db6400ff1d247b26",
   "engine/src/third_party/dart":"ce7c036db217b43014a05dcbdc377e3bcb7743ae",
-  "flutter":"2fdfa29e081bb368bf11b6177e4e9bb7c8ad4d34"
+  "flutter":"76dd29f6a819ad72393cb6670888ed3d2191c928"
 }
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