Optimization of bot comment commands

[purelind]

When we comment /cherry-pick-invite on cherry-picked pr to gain modify access of PR, If there are space characters in the comment command, the command will not take effect.

comment link pingcap/tiflow#10131 (comment)

[wuhuizuo]

When we comment /cherry-pick-invite on cherry-picked pr to gain modify access of PR, If there are space characters in the comment command, the command will not take effect.

comment link pingcap/tiflow#10131 (comment)

It's finished by inner lark channel.