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

diff --git a/Modules/_operator.c b/Modules/_operator.c
index dc67820..3bf8c12 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);