v2/handler: remove implemented TODO comment
v2/handler: remove implemented TODO comment

RyanTech/tchannel,Zirpon/tchannel,savaki/tchannel,bunnyblue/tchannel,Zirpon/tchannel,benfleis/tchannel,vanloswang/tchannel,sasa233/tchannel,hustxiaoc/tchannel,vanloswang/tchannel,i/tchannel,Zirpon/tchannel,bunnyblue/tchannel,sasa233/tchannel,chenwenbin928/tchannel,hustxiaoc/tchannel,benfleis/tchannel,savaki/tchannel,sasa233/tchannel,savaki/tchannel,benfleis/tchannel,chenwenbin928/tchannel,i/tchannel,RyanTech/tchannel,chenwenbin928/tchannel,hustxiaoc/tchannel,bunnyblue/tchannel,vanloswang/tchannel,i/tchannel,RyanTech/tchannel