Remove redundant test case test_uppercase_scheme

This test verifies that an upper case scheme ('HTTP') works correctly,
but this is already tested in `test_mixed_case_scheme_acceptable`.

test_requests.py

@@ -553,10 +553,6 @@ class RequestsTestCase(unittest.TestCase):
             'application/json'
         )
 
-    def test_uppercase_scheme(self):
-        r = requests.get('HTTP://example.com/')
-        self.assertEqual(r.status_code, 200)
-
     def test_uppercase_scheme_redirect(self):
         r = requests.get(httpbin('redirect-to'), params={'url': 'HTTP://example.com/'})
         self.assertEqual(r.status_code, 200)