chore: add comment for the workaround

Sometimes `brew upgrade` of Graphviz action fails on macOS runner while upgrading python packages.

This error is based on the below issue:
- actions/setup-python#577

Re-linking python will fix this problem:
- Ref: Homebrew/homebrew-core#165793 (comment)

.github/workflows/go.yml

@@ -32,6 +32,7 @@ jobs:
         if: matrix.os == 'macos-latest'
         run: |
           : # Workaround GitHub Actions Python issues
+          : # https://github.com/Homebrew/homebrew-core/issues/165793#issuecomment-1989441193
           brew unlink python && brew link --overwrite python
 
       - name: Set up Graphviz