Widen a suppression rule for sync_notifier::InvalidationNotifier::UpdateCredentials().

This change widens a suppression rule for Bug 118890 so it covers an occasional leak in sync_notifier::InvalidationNotifier::UpdateCredentials().

TBR=thakis
BUG=118890
TEST=make the "Linux Tests (valgrind)(6)" bot green.
Review URL: https://chromiumcodereview.appspot.com/10151012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@133869 0039d316-1c4b-4281-b951-d872f2087c98

tools/valgrind/memcheck/suppressions.txt

@@ -5312,7 +5312,6 @@
    bug_118890_a
    Memcheck:Leak
    ...
-   fun:_ZN27TestURLRequestContextGetter20GetURLRequestContextEv
    fun:_ZN8notifier18SingleLoginAttemptC1EPNS_13LoginSettingsEPNS0_8DelegateE
    fun:_ZN8notifier5Login15StartConnectionEv
    fun:_ZN13sync_notifier20InvalidationNotifier17UpdateCredentialsERKSsS2_