Call _PyImport_Fini to clean up c extensions

from_cpython/Python/import.c

@@ -600,7 +600,7 @@ _PyImport_FixupExtension(char *name, char *filename)
 {
     PyObject *modules, *mod, *dict, *copy;
     if (extensions == NULL) {
-        extensions = PyGC_RegisterStaticConstant(PyDict_New());
+        extensions = PyDict_New();
         if (extensions == NULL)
             return NULL;
     }

src/runtime/types.cpp

@@ -4811,6 +4811,7 @@ extern "C" void Py_Finalize() noexcept {
     PyGC_Collect();
 
     PyImport_Cleanup();
+    _PyImport_Fini();
 
 #ifdef Py_REF_DEBUG
     IN_SHUTDOWN = true;