Fix indentation in optimizer test

The test wasn't running because of an indentation mistake.

Author: fluhus

Lib/test/test_capi/test_opt.py

@@ -1531,7 +1531,7 @@ def f(n):
         # But all of the appends we care about are still there:
         self.assertEqual(uops.count("_CALL_LIST_APPEND"), len("ABCDEFG"))
 
-def test_narrow_type_to_constant_str_empty(self):
+    def test_narrow_type_to_constant_str_empty(self):
         def f(n):
             trace = []
             for i in range(n):