Revert of exclude SyncBackendRegistrarShutdownTest.BlockingShutdown from...

Revert of exclude SyncBackendRegistrarShutdownTest.BlockingShutdown from Dr.Memory bots (patchset #1 id:1 of https://codereview.chromium.org/668063002/)

Reason for revert:
the excluded test SyncBackendRegistrarShutdownTest.BlockingShutdown is removed

Original issue's description:
> exclude SyncBackendRegistrarShutdownTest.BlockingShutdown from Dr.Memory bots
>
> BUG=425568
> TBR=stanisc@chromium.org
> NOTRY=true
>
> Committed: https://crrev.com/f4efb8d1513eb996cf0f0f1f842a8c729ce2a098
> Cr-Commit-Position: refs/heads/master@{#300552}

TBR=stanisc@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=425568

Review URL: https://codereview.chromium.org/674433002

Cr-Commit-Position: refs/heads/master@{#300556}

tools/valgrind/gtest_exclude/unit_tests.gtest-drmemory_win32.txt

@@ -79,6 +79,3 @@ TranslateManagerRenderViewHostTest.*
 SafeBrowsingModuleVerifierWinTest.VerifyModuleExportModified
 SafeBrowsingModuleVerifierWinTest.VerifyModuleModified
 SafeBrowsingModuleVerifierWinTest.VerifyModuleUnmodified
-
-# http://crbug.com/425568
-SyncBackendRegistrarShutdownTest.BlockingShutdown