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

…aks between Python 3.12alpha3 (still working) and 3.12alpha6 (broken):

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

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

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

See also: python/cpython#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():