GH-108362: Revert "GH-108362: Incremental GC implementation (GH-108038)" (#115132)

Revert "GH-108362: Incremental GC implementation (GH-108038)"

This reverts commit 36518e69d7.

Python/import.c

@@ -1030,7 +1030,7 @@ _extensions_cache_set(PyObject *filename, PyObject *name, PyModuleDef *def)
     if (!already_set) {
         /* We assume that all module defs are statically allocated
            and will never be freed.  Otherwise, we would incref here. */
-        _Py_SetImmortal((PyObject *)def);
+        _Py_SetImmortal(def);
     }
     res = 0;