Exclude `front_end/third_party` from GRDP file checks
Exclude `front_end/third_party` from GRDP file checks

No files in here are able to call our language funcs so there's no point
wasting effort checking them.

Change-Id: I006cb81a32a39fd099ea44869335dd81a8d3f734
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2094122
Auto-Submit: Jack Franklin <993fcadce4d04090da2fefd557a0995e7966c8d5@chromium.org>
Commit-Queue: Paul Lewis <8915f5d5c39a08c5a3e8a8d7314756e4580816f9@chromium.org>
Reviewed-by: Paul Lewis <8915f5d5c39a08c5a3e8a8d7314756e4580816f9@chromium.org>

ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend