bpo-20891: Reenable test_embed.test_bpo20891() (GH-5420)

diff --git a/Lib/test/test_embed.py b/Lib/test/test_embed.py
index c9b6548..c7f45b5 100644
--- a/Lib/test/test_embed.py
+++ b/Lib/test/test_embed.py
@@ -198,9 +198,6 @@
         self.assertEqual(out, '')
         self.assertEqual(err, '')
 
-    @unittest.skipIf(True,
-                     "FIXME: test fails randomly because of a race conditon, "
-                     "see bpo-20891")
     def test_bpo20891(self):
         """
         bpo-20891: Calling PyGILState_Ensure in a non-Python thread before