Summary:
Recent Github actions of format checking fail due to invalid location
from where clang-format-diff.py is downloaded. Update the path to point
to a stable, archived location.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7944

Test Plan: manually check the result of Github action.

Reviewed By: ltamasi

Differential Revision: D26345066

Pulled By: riversand963

fbshipit-source-id: 2b1a58c2e59c2f1eb11202d321d2ea002cb0917e