correct grep to accept c++ files rather than rejecting them

1 job for !960 with clang-format-gitlab-ci in 1 minute and 14 seconds (queued for 25 seconds)
detached
Status Name Job ID Coverage
  Build
failed clang_format #118461

00:01:14

 
Name Stage Failure
failed
clang_format Build
2021-07-17 03:04:38 (60.3 MB/s) - '.clang-format' saved [2547/2547]

$ git diff-tree --no-commit-id --name-only -r origin/$CI_MERGE_REQUEST_TARGET_BRANCH_NAME -r $CI_COMMIT_SHA | grep -P '[.](c|cc|cpp|hpp|h)$'| xargs clang-format-11 -i
No such file or directory
No such file or directory
No such file or directory
No such file or directory
Cleaning up file based variables
ERROR: Job failed: exit code 1