Revert "Disabling flaky test TestSBUpdateCookies"

This reverts commit 9fedcd68.

Reason for revert: fixed after r560938

Original change's description:
> Disabling flaky test TestSBUpdateCookies
> 
> Full test name:
> SafeBrowsingDatabaseManagerCookieTest.TestSBUpdateCookies
> 
> Link to failure:
> https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/linux-xenial-rel/54
> 
> Bug: 842195
> Change-Id: I807a6815fc65e75b3023095d8abd875ad2cf3e14
> 
> TBR=jialiul@chromium.org
> 
> Change-Id: I807a6815fc65e75b3023095d8abd875ad2cf3e14
> Reviewed-on: https://chromium-review.googlesource.com/1055618
> Reviewed-by: Tommy Martino <tmartino@chromium.org>
> Commit-Queue: Tommy Martino <tmartino@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#557905}

TBR=tmartino@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 842195
Change-Id: I1dfc6104223cc0ae27fb912d20befb98d77aa616
Reviewed-on: https://chromium-review.googlesource.com/1071848Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: John Abd-El-Malek <jam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#561546}

chrome/browser/safe_browsing/safe_browsing_service_browsertest.cc

@@ -2174,17 +2174,10 @@ class SafeBrowsingDatabaseManagerCookieTest : public InProcessBrowserTest {
   DISALLOW_COPY_AND_ASSIGN(SafeBrowsingDatabaseManagerCookieTest);
 };
 
-// TODO(crbug.com/842195): This is flaky on Ubuntu.
-#if defined(OS_LINUX)
-#define MAYBE_TestSBUpdateCookies DISABLED_TestSBUpdateCookies
-#else
-#define MAYBE_TestSBUpdateCookies TestSBUpdateCookies
-#endif
-
 // Test that a Local Safe Browsing database update request both sends cookies
 // and can save cookies.
 IN_PROC_BROWSER_TEST_F(SafeBrowsingDatabaseManagerCookieTest,
-                       MAYBE_TestSBUpdateCookies) {
+                       TestSBUpdateCookies) {
   base::RunLoop run_loop;
   auto callback_subscription =
       sb_factory_->test_safe_browsing_service()