Fixup for failing Beta CI (#2092)

Turns out, we shipped a new Flutter beta as well. 

Commenting out `experimental/varfont_shader_puzzle` from beta CI

Everything else is just cleanup.

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-devrel
channel on [Discord].

<!-- Links -->
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[CLA]: https://cla.developers.google.com/
[Discord]: https://github.com/flutter/flutter/wiki/Chat
[Contributors Guide]:
https://github.com/flutter/samples/blob/main/CONTRIBUTING.md

isolate_example/.metadata

@@ -4,8 +4,8 @@
 # This file should be version controlled and should not be manually edited.
 
 version:
-  revision: "adc7dfe87ebc5ff6cb6ceb786efaa83058fdc1a1"
-  channel: "beta"
+  revision: "db7ef5bf9f59442b0e200a90587e8fa5e0c6336a"
+  channel: "stable"
 
 project_type: app
 
@@ -13,23 +13,23 @@ project_type: app
 migration:
   platforms:
     - platform: root
-      create_revision: adc7dfe87ebc5ff6cb6ceb786efaa83058fdc1a1
-      base_revision: adc7dfe87ebc5ff6cb6ceb786efaa83058fdc1a1
+      create_revision: db7ef5bf9f59442b0e200a90587e8fa5e0c6336a
+      base_revision: db7ef5bf9f59442b0e200a90587e8fa5e0c6336a
     - platform: android
-      create_revision: adc7dfe87ebc5ff6cb6ceb786efaa83058fdc1a1
-      base_revision: adc7dfe87ebc5ff6cb6ceb786efaa83058fdc1a1
+      create_revision: db7ef5bf9f59442b0e200a90587e8fa5e0c6336a
+      base_revision: db7ef5bf9f59442b0e200a90587e8fa5e0c6336a
     - platform: ios
-      create_revision: adc7dfe87ebc5ff6cb6ceb786efaa83058fdc1a1
-      base_revision: adc7dfe87ebc5ff6cb6ceb786efaa83058fdc1a1
+      create_revision: db7ef5bf9f59442b0e200a90587e8fa5e0c6336a
+      base_revision: db7ef5bf9f59442b0e200a90587e8fa5e0c6336a
     - platform: linux
-      create_revision: adc7dfe87ebc5ff6cb6ceb786efaa83058fdc1a1
-      base_revision: adc7dfe87ebc5ff6cb6ceb786efaa83058fdc1a1
+      create_revision: db7ef5bf9f59442b0e200a90587e8fa5e0c6336a
+      base_revision: db7ef5bf9f59442b0e200a90587e8fa5e0c6336a
     - platform: macos
-      create_revision: adc7dfe87ebc5ff6cb6ceb786efaa83058fdc1a1
-      base_revision: adc7dfe87ebc5ff6cb6ceb786efaa83058fdc1a1
+      create_revision: db7ef5bf9f59442b0e200a90587e8fa5e0c6336a
+      base_revision: db7ef5bf9f59442b0e200a90587e8fa5e0c6336a
     - platform: windows
-      create_revision: adc7dfe87ebc5ff6cb6ceb786efaa83058fdc1a1
-      base_revision: adc7dfe87ebc5ff6cb6ceb786efaa83058fdc1a1
+      create_revision: db7ef5bf9f59442b0e200a90587e8fa5e0c6336a
+      base_revision: db7ef5bf9f59442b0e200a90587e8fa5e0c6336a
 
   # User provided section