remove unused pkg. (#122)

* feat: update max Seq format method.

* update Format method in pb.

* update to correct constant.

* update format method in pb.

* feat: update conversation fields.

* update pb files.

* update ConversationsDestructMsgs method.

* update conversation and msg destruct pb.

* feat: update GroupInfoForSetEX struct.

* update group pb.

* feat: implement request max count limit.

* feat: add PushMsgReq

* remove unused pkg.

group/group.go

@@ -17,7 +17,6 @@ package group
 import (
 	"errors"
 	"fmt"
-	"github.com/openimsdk/protocol/constant"
 )
 
 func (x *CreateGroupReq) Check() error {