Re-enable ChromeVoxBackground*.NavigationSyncSelect

Mostly speculative; pass with

testing/xvfb.py out/d/browser_tests --gtest_filter=ChromeVox*.NavigationSyncsSelect
!! & !! & !! & !! &

TBR=dtseng@chromium.org

Fixed: 976105
Change-Id: Ieb646dd0ab22d4b45f2355c89542a59c51af5888
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2209684Reviewed-by: David Tseng <dtseng@chromium.org>
Commit-Queue: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#770789}

chrome/browser/resources/chromeos/accessibility/chromevox/background/background_test.js

@@ -1582,7 +1582,7 @@ TEST_F('ChromeVoxBackgroundTest', 'NavigationEscapesEdit', function() {
       });
 });
 
-TEST_F('ChromeVoxBackgroundTest', 'DISABLED_NavigationSyncsSelect', function() {
+TEST_F('ChromeVoxBackgroundTest', 'NavigationSyncsSelect', function() {
   const mockFeedback = this.createMockFeedback();
   this.runWithLoadedTree(
       `