Replace Py_NotImplemented returns with the macro form Py_RETURN_NOTIMPLEMENTED.
The macro was introduced in #12724.
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index bef2abf..0918671 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -7417,8 +7417,7 @@
         return v;
     }
 
-    Py_INCREF(Py_NotImplemented);
-    return Py_NotImplemented;
+    Py_RETURN_NOTIMPLEMENTED;
 }
 
 int
@@ -9291,10 +9290,8 @@
 static PyObject *
 unicode_mod(PyObject *v, PyObject *w)
 {
-    if (!PyUnicode_Check(v)) {
-        Py_INCREF(Py_NotImplemented);
-        return Py_NotImplemented;
-    }
+    if (!PyUnicode_Check(v))
+        Py_RETURN_NOTIMPLEMENTED;
     return PyUnicode_Format(v, w);
 }