Decreased memory requirements of new tests added in issue21448.

Lib/test/test_email/test_email.py

@@ -3406,7 +3406,8 @@ class TestFeedParsers(TestEmailBase):
         self.assertEqual(m.items(), [('a', ''), ('b', '\x85'), ('c', '')])
 
     def test_long_lines(self):
-        M, N = 1000, 100000
+        # Expected peak memory use on 32-bit platform: 6*N*M bytes.
+        M, N = 1000, 20000
         m = self.parse(['a:b\n\n'] + ['x'*M] * N)
         self.assertEqual(m.items(), [('a', 'b')])
         self.assertEqual(m.get_payload(), 'x'*M*N)