Revert "Disable flaky test AccessibilityIpcErrorBrowserTest.ResetBrowserAccessibilityManager"

This reverts commit 6e65ba90.

Reason for revert:

Findit (https://goo.gl/kROfz5) identified CL at revision 669034 as the
culprit for flakes in the build cycles as shown on:
https://analysis.chromium.org/p/chromium/flake-portal/analysis/culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyQwsSDEZsYWtlQ3VscHJpdCIxY2hyb21pdW0vNmU2NWJhOTA3ZjUyMGNlZmU5YjYyMDg3MWNmZmIyZTc1N2NhNmQ2Nww

Sample Failed Build: https://ci.chromium.org/buildbot/chromium.linux/Linux%20Tests%20%28dbg%29%281%29%2832%29/59319

Sample Failed Step: content_browsertests

Sample Flaky Test: AccessibilityIpcErrorBrowserTest.DISABLE_ResetBrowserAccessibilityManager

Original change's description:
> Disable flaky test AccessibilityIpcErrorBrowserTest.ResetBrowserAccessibilityManager
> 
> TBR=kschmi@microsoft.com
> 
> Bug: 973946
> 
> Change-Id: I69b54fdfe9421acacaf98c2bcf684680e7cb66fd
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1659029
> Commit-Queue: Oksana Zhuravlova <oksamyt@chromium.org>
> Reviewed-by: Kurt Catti-Schmidt <kschmi@microsoft.com>
> Cr-Commit-Position: refs/heads/master@{#669034}


Change-Id: Ic5a44c3d23a11cd0f209a6143067d51e803a617a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 973946
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1660008
Cr-Commit-Position: refs/heads/master@{#669100}

content/browser/accessibility/accessibility_ipc_error_browsertest.cc

@@ -39,9 +39,8 @@ class AccessibilityIpcErrorBrowserTest : public ContentBrowserTest {
   DISALLOW_COPY_AND_ASSIGN(AccessibilityIpcErrorBrowserTest);
 };
 
-// Flaky on all platforms. http://crbug.com/973946
 IN_PROC_BROWSER_TEST_F(AccessibilityIpcErrorBrowserTest,
-                       DISABLE_ResetBrowserAccessibilityManager) {
+                       ResetBrowserAccessibilityManager) {
   // Create a data url and load it.
   const char url_str[] =
       "data:text/html,"