gitignore: Remove webrtc/

Since webrtc/* has been moved to the top level
we should ignore it so it can be easily cleaned.
Right now there are usually at least .pyc files.

BUG=chromium:611808
NOTRY=True

Change-Id: If04284353a4e467583f810b2e5423c32269ba3cf
Reviewed-on: https://webrtc-review.googlesource.com/1571
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Henrik Kjellander <kjellander@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#19851}
diff --git a/.gitignore b/.gitignore
index c1e6b5d..ce0a07a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -63,3 +63,4 @@
 /rtc_tools/testing/golang/*/*.zip
 /x86-generic_out/
 /xcodebuild
+!webrtc/*