Add internal test grd to internal_grds list.

Test grd simulates a grd with a part file that doesn't exist for unit
tests. This same grd is also analyzed by the translation script when run
for real, so it should also be ignored.

Bug: 961345
Change-Id: I5808e814ed59dbbf41b158057adcbbc67e3e5892
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1602595Reviewed-by: Mustafa Emre Acer <meacer@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Bruno Santos <brunoad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#658256}

tools/gritsettings/translation_expectations.pyl

@@ -98,5 +98,7 @@
   # not be checked by translation script.
   "internal_grds": [
     "chrome/browser/resources/kiosk_next_internal_resources.grd",
+    # Test grd that contains a part file that doesn't exist.
+    "tools/translation/testdata/internal.grd",
   ],
 }