Clean up GitHub Actions workflow files in old branches

[desrosj]

#64227/[61286] introduced a new Grunt task that cleans up workflow files in old branches.

While the changes to the Grunt.js file should not necessarily be backported, the task defines and ensures the ideal state of the .github/workfows directory for newly created branches.

For the sake of consistency, all old branches should be updated to remove any of these now deleted workflow files that remain.