Run gc.collect() twice in test_rename on Python 3.12

Recently, the conditional `gc.collect()` step for Python >= 3.12 in
`TestSubmodule.test_rename` is often insufficient. This has mainly
been seen in #2248. For example:

https://github.com/gitpython-developers/GitPython/actions/runs/22864869684/job/66331124651?pr=2106#step:12:620

In principle, there can be situations with finalizers where a cycle
is only collectable due to finalization that happened due to a
previous collection. Therefore, there is occasionally a benefit to
collecting twice. This does that, in the hope that it will help.

Author: EliahKagan

test/test_submodule.py

@@ -1011,6 +1011,7 @@ def test_rename(self, rwdir):
         # garbage collector detailed in https://github.com/python/cpython/issues/97922.)
         if sys.platform == "win32" and sys.version_info >= (3, 12):
             gc.collect()
+            gc.collect()  # Some finalizer scenarios need two collections, at least in theory.
 
         new_path = "renamed/myname"
         assert sm.move(new_path).name == new_path