clang-tidy: Remove `.clang-tidy`

Having `.clang-tidy` file will force the presubmit to compile the code
with clang. While the code generated by script can't be compiled by
clang (reason unknown).

Tested: Buildable

Google-Bug-Id: 299895444
Google-Bug-Id: 298918774
Change-Id: I95819db8b4cc8965af882095d9b17f53876d7852
Signed-off-by: Michael Shen <gpgpgp@google.com>