Exclude ios/net from the base::Bind exceptions in PRESUBMIT.

Conversion is complete and exception is no longer needed.

Bug: 1007794
Change-Id: I53ca46ad6405f9de6792d022c7d4416509cc025d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2503808
Commit-Queue: Renjie Tang <renjietang@chromium.org>
Auto-Submit: Renjie Tang <renjietang@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821336}

PRESUBMIT.py

@@ -391,7 +391,6 @@ _NOT_CONVERTED_TO_MODERN_BIND_AND_CALLBACK = '|'.join((
   '^google_apis/drive/',
   '^ios/chrome/',
   '^ios/components/',
-  '^ios/net/',
   '^ios/web/',
   '^ios/web_view/',
   '^ipc/',