pythongh-128729: Fix RuntimeWarning in test_unittest (pythonGH-128730)

Author: serhiy-storchaka

Lib/test/test_unittest/test_case.py

@@ -347,7 +347,10 @@ async def test1(self):
                 return 1
 
         with self.assertWarns(DeprecationWarning) as w:
+            warnings.filterwarnings('ignore',
+                    'coroutine .* was never awaited', RuntimeWarning)
             Foo('test1').run()
+            support.gc_collect()
         self.assertIn('It is deprecated to return a value that is not None', str(w.warning))
         self.assertIn('test1', str(w.warning))
         self.assertEqual(w.filename, __file__)