gh-133210: Fix test_types with --without-doc-strings

[sobolevn]

When compiled with --without-doc-strings:

» ./python.exe -m test test_types
Using random seed: 2821981553
0:00:00 load avg: 10.13 Run 1 test sequentially in a single process
0:00:00 load avg: 10.13 [1/1] test_types
test test_types failed -- Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_types.py", line 717, in test_frame_locals_proxy_type
    self.assertIsInstance(types.FrameLocalsProxyType.__doc__, str)
    ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: None is not an instance of <class 'str'>

0:00:00 load avg: 10.13 [1/1/1] test_types failed (1 failure)

• Issue: Some tests fail when python is compiled with --without-doc-strings #133210

[sobolevn]

No backports are needed, because this is 3.15+ only: 8f59fbb