Make the net::URLFetcher presubmit check not require a presubmit bypass

I misunderstood the boolean parameter. This check is intended to be
advisory, rather than something that blocks landing CLs.

Bug: 746977, 598073
Change-Id: Ib7695f7bea15f1613a4f9e73e0258fa231340161
Reviewed-on: https://chromium-review.googlesource.com/992393Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Matt Menke <mmenke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548394}

PRESUBMIT.py

@@ -552,7 +552,7 @@ _BANNED_CPP_FUNCTIONS = (
         'net::URLFetcher may still be used in binaries that do not embed',
         'content.',
       ),
-      True,
+      False,
       (
         r'^ios[\\\/].*\.(cc|h)$',
         r'.*[\\\/]ios[\\\/].*\.(cc|h)$',