GH-111485: Silence warnings in Python/executor_cases.c.h (#111619)

Python/generated_cases.c.h

@@ -1743,6 +1743,8 @@
                 STAT_INC(UNPACK_SEQUENCE, deferred);
                 DECREMENT_ADAPTIVE_COUNTER(this_instr[1].cache);
                 #endif  /* ENABLE_SPECIALIZATION */
+                (void)seq;
+                (void)counter;
             }
             // _UNPACK_SEQUENCE
             {