Valgrind: Remove an obsolete suppression AutomationProxyTest which no longer exists.

BUG=122733
NOTRY=true
TBR=benwells@chromium.org

Review URL: https://codereview.chromium.org/90363002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237494 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237494