Fix a compile warning in dictobject.c (GH-16610)

diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 5c3f1fb..164fe2a 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -4186,7 +4186,6 @@
     Py_ssize_t len_self;
     int rv;
     int (*dict_contains)(_PyDictViewObject *, PyObject *);
-    PyObject *tmp;
 
     /* Python interpreter swaps parameters when dict view
        is on right side of & */