Fix unittest method usage that was long deprecated and removed in Py3.11.

tests/run/test_grammar.py

@@ -895,7 +895,7 @@ class GrammarTests(unittest.TestCase):
         def g(): f((yield from ()), 1)
         # Do not require parenthesis for tuple unpacking
         def g(): rest = 4, 5, 6; yield 1, 2, 3, *rest
-        self.assertEquals(list(g()), [(1, 2, 3, 4, 5, 6)])
+        self.assertEqual(list(g()), [(1, 2, 3, 4, 5, 6)])
         check_syntax_error(self, "def g(): f(yield 1)")
         check_syntax_error(self, "def g(): f(yield 1, 1)")
         check_syntax_error(self, "def g(): f(yield from ())")