Fix clang-format presubmit check
Fix clang-format presubmit check

I half-broke the check when updating the docker containers. The new
docker container does not have a symlink from `clang-format` to
`clang-format-9`, so we have to call `clang-format-9` instead.

This was already correct for the `clang-format-diff-9` call - that's why
it was only half-broken.

google/orbit,google/orbit,google/orbit,google/orbit