Correctly ignore osx_framework_user mismatches

The expected 'headers' path is generally:

* distutils (old): $PREFIX/include/python3.8/$PROJECT
* sysconfig (new): $PREFIX/include/$PROJECT

So we should check whether the old value's parent is a pythonX.Y, and
the new value's parent matches the old's second-level parent.

src/pip/_internal/locations/__init__.py

@@ -185,8 +185,8 @@ def get_scheme(
             user
             and is_osx_framework()
             and k == "headers"
-            and old_v.parent == new_v
-            and old_v.name.startswith("python")
+            and old_v.parent.parent == new_v.parent
+            and old_v.parent.name.startswith("python")
         )
         if skip_osx_framework_user_special_case:
             continue