渲染有bug，dropout掉的内容未从标签中剔除

[KingHaremIII]

core/layout/init.py中添加：
waiting_removing = [] # 添加
for block in self.block_list:
if np.random.rand() < dropout:
log.info('dropout incurred. ')
waiting_removing.append(block) # 添加
continue

block渲染完后删除dropout掉的标签：
for wr in waiting_removing:
self.block_list.remove(wr)

[BboyHanat]

我debug 下，欢迎pr 哈