Rust_toolchain upgrade fails

[nicolecheetham]

The semi-automatic script no longer works when upgrading rust_toolchain. It specifically outputs an error message stating WORKSPACE has to be enabled for sync command to work, run with --enable_workspace.

What has been done:
In the rust_toolchain upgrade.py file the flag was added to the sync command on line 34. However, when the new_release script is rerun it warns workspace support will be removed in the near future, mentions switching to MODULE style externals like bzlmod, and then errors out as the subprocess returned a non-zero exit status.