No longer use devtools path in presubmit test

DevTools frontend is moving to a separate repository and pulled
into a separate path. It would be nice to have this test not point
to a non-existent path (even though the file does not exist either).

Change-Id: Id5ce7cd3057617fd5880968cb7aab3ec064fe5d5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1840235
Commit-Queue: Yang Guo <yangguo@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Cr-Commit-Position: refs/heads/master@{#703222}

third_party/blink/PRESUBMIT_test.py

@@ -240,7 +240,7 @@ class CxxDependencyTest(unittest.TestCase):
 
     # External module checks should not affect CSS files.
     def testCheckCSSIgnored(self):
-        filename = 'third_party/blink/renderer/devtools/front_end/timeline/someFile.css'
+        filename = 'third_party/blink/renderer/someFile.css'
         errors = self.runCheck(filename, ['.toolbar::after { color: pink; }\n'])
         self.assertEqual([], errors)