Remove unused function in presubmit script

FilterFiles function is defined but unused in the code.

BUG=

R=machenbach@chromium.org

Review URL: https://codereview.chromium.org/1364643002

Cr-Commit-Position: refs/heads/master@{#30882}

AUTHORS

@@ -92,6 +92,7 @@ Rene Rebe <rene@exactcode.de>
 Robert Mustacchi <rm@fingolfin.org>
 Robert Nagy <robert.nagy@gmail.com>
 Ryan Dahl <ry@tinyclouds.org>
+Sakthipriyan Vairamani (thefourtheye) <thechargingvolcano@gmail.com>
 Sandro Santilli <strk@keybit.net>
 Sanjoy Das <sanjoy@playingwithpointers.com>
 Seo Sanghyeon <sanxiyn@gmail.com>

PRESUBMIT.py

@@ -233,7 +233,6 @@ def _SkipTreeCheck(input_api, output_api):
   """Check the env var whether we want to skip tree check.
      Only skip if include/v8-version.h has been updated."""
   src_version = 'include/v8-version.h'
-  FilterFile = lambda file: file.LocalPath() == src_version
   if not input_api.AffectedSourceFiles(
       lambda file: file.LocalPath() == src_version):
     return False