[test] Un-XFAIL TestRaise.RaiseTestCase.test_restart_bug

This test was marked as an expected failure because of PR20231 but it
seems to consistently result in an unexpected success across the bots.
Let's try to re-enable this test again.

llvm-svn: 324227

lldb/packages/Python/lldbsuite/test/functionalities/signal/raise/TestRaise.py

@@ -189,10 +189,6 @@ class RaiseTestCase(TestBase):
         # reset signal handling to default
         self.set_handle(signal, default_pass, default_stop, default_notify)
 
-    @expectedFailureAll(
-        oslist=["linux"] +
-        getDarwinOSTriples(),
-        bugnumber="llvm.org/pr20231")
     def test_restart_bug(self):
         """Test that we catch a signal in the edge case where the process receives it while we are
         about to interrupt it"""