make indentation match other files

(Actually by Matthew, but setting Claire as the author so
that it will be easier to see via `git blame` in the future
if I mangle Claire's code.)

racket/src/racket/src/letrec_check.c

@@ -1285,6 +1285,8 @@ Scheme_Object *letrec_check_set(Scheme_Object *o, Letrec_Check_Frame *frame,
   sb = (Scheme_Set_Bang *)o;
   val = sb->val;
 
+
+
   val = letrec_check_expr(val, frame, uvars, pvars, pos);
   sb->val = val;