Remove Mac-only suppression in ExtensionPrefStoreTest, now fixed....

tools/valgrind/memcheck/suppressions_mac.txt

Index: tools/valgrind/memcheck/suppressions_mac.txt
===================================================================
--- tools/valgrind/memcheck/suppressions_mac.txt	(revision 53622)
+++ tools/valgrind/memcheck/suppressions_mac.txt	(working copy)
@@ -1372,16 +1372,6 @@
    fun:_ZN18FocusIndicationFix40currentOSHasSetFocusRingStyleInBitmapBugEv
 }
 {
-   bug_48980_mac
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZNSt8_Rb_treeIPN11PrefService10PreferenceES2_St9_IdentityIS2_ENS0_24PreferencePathComparatorESaIS2_EE9_M_insertEPSt18_Rb_tree_node_baseS9_RKS2_
-   fun:_ZNSt8_Rb_treeIPN11PrefService10PreferenceES2_St9_IdentityIS2_ENS0_24PreferencePathComparatorESaIS2_EE13insert_uniqueERKS2_
-   fun:_ZNSt3setIPN11PrefService10PreferenceENS0_24PreferencePathComparatorESaIS2_EE6insertERKS2_
-   fun:_ZN11PrefService18RegisterPreferenceEPNS_10PreferenceE
-   fun:_ZN44ExtensionPrefStoreTest_NotifyWhenNeeded_Test8TestBodyEv
-}
-{
    bug_49250_a
    Memcheck:Cond
    fun:gleUpdateFogData