Change duplicate test file presubmit check to ignore deletes.

In javascript and pixel tests, there should not be .in and .pdf files
with the same name. There is a presubmit check to enforce this, but it
does not understand file deletions. So if one deletes foo.pdf and add
foo.in in the same CL, the presubmit check will fail. Fix this by
ignoring file deletions in the presubmit check.

Change-Id: I59cc04884f25852e5db749c6242ee4857bbc7a71
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/60571
Reviewed-by: Nicolás Peña Moreno <npm@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index ec0f0e4..0567def 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -270,6 +270,8 @@
   tests_added = []
   results = []
   for f in input_api.AffectedFiles():
+    if f.Action() == 'D':
+      continue
     if not f.LocalPath().startswith(('testing/resources/pixel/',
         'testing/resources/javascript/')):
       continue