gh-120437: Fix _CHECK_STACK_SPACE optimization problems introduced in gh-118322 (GH-120712)

Co-authored-by: Ken Jin <kenjin4096@gmail.com>

Python/optimizer_bytecodes.c

@@ -601,7 +601,6 @@ dummy_func(void) {
         (void)callable;
         (void)self_or_null;
         (void)args;
-        first_valid_check_stack = NULL;
         new_frame = NULL;
         ctx->done = true;
     }