Revert of Suppress Uninitialized access in ExtensionManagement::Refresh...

Revert of Suppress Uninitialized access in ExtensionManagement::Refresh (patchset #2 id:20001 of https://codereview.chromium.org/608063002/)

Reason for revert:
The Clang roll that caused the Valgrind error was reverted in https://chromium.googlesource.com/chromium/src/+/3c80ac9fd48da3d11852eecd6999053d6d84c56c

Original issue's description:
> Suppress Uninitialized access in ExtensionManagement::Refresh
>
> BUG=418234
> TBR=miu@chromium.org
>
> Committed: https://crrev.com/459b9796ff2ba105e8a6bae4c7e63508ea83bb67
> Cr-Commit-Position: refs/heads/master@{#297028}

TBR=miu@chromium.org,oshima@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=418234

Review URL: https://codereview.chromium.org/610753002

Cr-Commit-Position: refs/heads/master@{#297074}

tools/valgrind/memcheck/suppressions.txt

@@ -3453,9 +3453,3 @@
    fun:_ZN4base19SequencedWorkerPoolC1EmRKSs
    fun:_ZN16sync_file_system13drive_backend14SyncEngineTest5SetUpEv
 }
-{
-   bug_418234
-   Memcheck:Uninitialized
-   fun:_ZN10extensions19ExtensionManagement7RefreshEv
-   fun:_ZN10extensions19ExtensionManagement22OnExtensionPrefChangedEv
-}