Add explicit shell: bash to validate-go-version workflow step

[Copilot]

Addresses review comment r3503367385 on #8906. The "Validate Go version consistency" step relies on bash-specific features (read -d '' and process substitution < <(...)), which are not guaranteed if the default runner shell changes.

Changes

• Add shell: bash to the Validate Go version consistency step in .github/workflows/validate-go-version.yml, making the bash dependency explicit.

      - name: Validate Go version consistency
        shell: bash
        run: |
          ...

[microsoft-github-policy-service]

Hi @@copilot. Thank you for your interest in helping to improve the Azure Developer CLI experience and for your contribution. We've noticed that there hasn't been recent engagement on this pull request. If this is still an active work stream, please let us know by pushing some changes or leaving a comment. Otherwise, we'll close this out in 7 days.

[microsoft-github-policy-service]

Hi @@copilot. Thank you for your contribution. Since there hasn't been recent engagement, we're going to close this out. Feel free to respond with a comment containing "/reopen" if you'd like to continue working on these changes. Please be sure to use the command to reopen or remove the "no-recent-activity" label; otherwise, this is likely to be closed again with the next cleanup pass.