executor: remove Next() function for CancelDDLJobsExec (#6060)
executor: remove Next() function for CancelDDLJobsExec (#6060)


tiancaiamao/tidb,wusphinx/tidb,Nify/tidb,kyle-wang/tidb,ngaut/tidb,ngaut/tidb,ming-relax/tidb,kyle-wang/tidb,pingcap/tidb,cosmtrek/tidb,tiancaiamao/tidb,c4pt0r/tidb,coocood/tidb,c4pt0r/tidb,ngaut/tidb,Nify/tidb,qiuyesuifeng/tidb,kyle-wang/tidb,EvilMcJerkface/tidb,coocood/tidb,kyle-wang/tidb,Cofyc/tidb,Cofyc/tidb,c4pt0r/tidb,pingcap/tidb,ming-relax/tidb,XuHuaiyu/tidb,qiuyesuifeng/tidb,XuHuaiyu/tidb,ngaut/tidb,cosmtrek/tidb,wusphinx/tidb,c4pt0r/tidb,ngaut/tidb,pingcap/tidb,EvilMcJerkface/tidb,pingcap/tidb,pingcap/tidb,pingcap/tidb,c4pt0r/tidb,kyle-wang/tidb,ngaut/tidb,mccxj/tidb,kyle-wang/tidb,mccxj/tidb,CodeRushing/tidb,c4pt0r/tidb,CodeRushing/tidb