thread_sync.c: document SizedQueue#clear correctly [ci skip]

* thread_sync.c (rb_szqueue_clear): fix class name in RDoc

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58511 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

thread_sync.c

@@ -1066,7 +1066,7 @@ rb_szqueue_pop(int argc, VALUE *argv, VALUE self)
 }
 
 /*
- * Document-method: Queue#clear
+ * Document-method: SizedQueue#clear
  *
  * Removes all objects from the queue.
  */