Cleanup: Remove bug_chomper entry from .gitignore.

This is not necessary anymore, now that bug_chomper was moved into
skia.googlesource.com/buildbot.git

BUG=None
TBR=borenet@google.com

Review URL: https://codereview.chromium.org/748363002
diff --git a/.gitignore b/.gitignore
index f6adb6e..532a2cc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,7 +15,6 @@
 platform_tools/chromeos/third_party/externals
 platform_tools/chromeos/toolchain
 third_party/externals
-tools/bug_chomper/oauth_client_secret.json
 tools/skp/page_sets/data/*.json
 tools/skp/page_sets/data/*.wpr
 xcodebuild