bpo-35303: Fix a reference leak in _operator.c's methodcaller_repr(). (GH-10689)

(cherry picked from commit 5b83ef71d3060e1651d3680e805f13a1049c7d6d)

Co-authored-by: Zackery Spytz <zspytz@gmail.com>
diff --git a/Modules/_operator.c b/Modules/_operator.c
index f2fd656..51daa1f 100644
--- a/Modules/_operator.c
+++ b/Modules/_operator.c
@@ -1583,6 +1583,7 @@
                 goto done;
             if (i >= numtotalargs) {
                 i = -1;
+                Py_DECREF(onerepr);
                 break;
             }
             PyTuple_SET_ITEM(argreprs, i, onerepr);