Fix Homebrew undent warning
Fix Homebrew undent warning

Update the generated `dart.rb` formula file to fix:

```
Warning: Calling <<-EOS.undent is deprecated!
Use <<~EOS instead.
/usr/local/Homebrew/Library/Taps/dart-lang/homebrew-dart/dart.rb:72:in `caveats'
Please report this to the dart-lang/dart tap!
```

being reported by `brew`.

Fixes https://github.com/dart-lang/homebrew-dart/issues/48

Credit for original patch to @fsouza:

https://github.com/fsouza/homebrew-dart/commit/06b76e0935a0c74e8f10d32b81e1b72358a661b4

Closes #32346
https://github.com/dart-lang/sdk/pull/32346

GitOrigin-RevId: 938a696caea21eda193375ad4cce5aab0e7b5e71
Change-Id: I757647a7ef0a373cb0258f0fcf03f89849aeba5e
Reviewed-on: https://dart-review.googlesource.com/44100
Reviewed-by: Kevin Moore <1d6e7d10d051cf619c5282da3c28fd8d3e0a65a4@google.com>
Reviewed-by: William Hesse <a821cddceae7dc400f272e3cb1a72f400f9fed6d@google.com>

dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk