Replace Py_NotImplemented returns with the macro form Py_RETURN_NOTIMPLEMENTED.
The macro was introduced in #12724.
diff --git a/Objects/classobject.c b/Objects/classobject.c
index 6df930f..b52a209 100644
--- a/Objects/classobject.c
+++ b/Objects/classobject.c
@@ -190,8 +190,7 @@
         !PyMethod_Check(self) ||
         !PyMethod_Check(other))
     {
-        Py_INCREF(Py_NotImplemented);
-        return Py_NotImplemented;
+        Py_RETURN_NOTIMPLEMENTED;
     }
     a = (PyMethodObject *)self;
     b = (PyMethodObject *)other;
@@ -516,8 +515,7 @@
         !PyInstanceMethod_Check(self) ||
         !PyInstanceMethod_Check(other))
     {
-        Py_INCREF(Py_NotImplemented);
-        return Py_NotImplemented;
+        Py_RETURN_NOTIMPLEMENTED;
     }
     a = (PyInstanceMethodObject *)self;
     b = (PyInstanceMethodObject *)other;