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: |
          ...