[CI] Re-enable clang-format workflow (#15839)
It looks like this has been disabled since September(!!) due to a bad
merge
[here](https://github.com/intel/llvm/commit/9379d84d1784fdac81b427508eb64a119fe82a5b#diff-6860ad0dc3584a2d702e231d5e9e9937e24f43777fd16954ce741eed68e94d50L12).
Thanks to Udit for finding this.
Signed-off-by: Sarnie, Nick <nick.sarnie@intel.com>
