Remove test code that does not exercise anything in pybind11, but breaks between…

Remove test code that does not exercise anything in pybind11, but breaks between Python 3.12alpha3 (still working) and 3.12alpha6 (broken): (#4559)

```
str(OrderedDict([(1, "a"), (2, "b")]))
```

Old:
```
OrderedDict([(1, 'a'), (2, 'b')])
```

New:
```
OrderedDict({1: 'a', 2: 'b'})
```

See also: https://github.com/python/cpython/issues/101446

tests/test_modules.py

@@ -63,7 +63,6 @@ def test_importing():
     from pybind11_tests.modules import OD
 
     assert OD is OrderedDict
-    assert str(OD([(1, "a"), (2, "b")])) == "OrderedDict([(1, 'a'), (2, 'b')])"
 
 
 def test_pydoc():