Run Providers/FileManagerBrowser test all bots

Persistent flake cause affecting all FileManager browser tests is fixed
by issue 831074 issue 804413 issue 829310.

Intermittent flake cause affecting Providers and other FileManger tests
is fixed by crrev.com/554647.

Run the Providers test all bots to help confirm issue 668680 is gone.

Bug: 668680,836254
Change-Id: Ib2eb38cddd454ae0671929da201c70a157f29308
Reviewed-on: https://chromium-review.googlesource.com/1034418
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Stuart Langley <slangley@chromium.org>
Cr-Commit-Position: refs/heads/master@{#554688}

chrome/browser/chromeos/file_manager/file_manager_browsertest.cc

@@ -508,13 +508,8 @@ WRAPPED_INSTANTIATE_TEST_CASE_P(
                       TestParameter(IN_GUEST_MODE, "showGridViewDownloads"),
                       TestParameter(NOT_IN_GUEST_MODE, "showGridViewDrive")));
 
-#if defined(DISABLE_SLOW_FILESAPP_TESTS)
-#define MAYBE_Providers DISABLED_Providers
-#else
-#define MAYBE_Providers Providers
-#endif
 WRAPPED_INSTANTIATE_TEST_CASE_P(
-    MAYBE_Providers,
+    Providers,
     FileManagerBrowserTest,
     ::testing::Values(
         TestParameter(NOT_IN_GUEST_MODE, "requestMount"),