Migrate "Channel.RemoveMember" to Sync by default (#11245)

* Migrate Channel.RemoveMember to Sync by default

* Address comments

app/channel.go

@@ -1616,8 +1616,8 @@ func (a *App) removeUserFromChannel(userIdToRemove string, removerUserId string,
 		return err
 	}
 
-	if cmresult := <-a.Srv.Store.Channel().RemoveMember(channel.Id, userIdToRemove); cmresult.Err != nil {
-		return cmresult.Err
+	if err := a.Srv.Store.Channel().RemoveMember(channel.Id, userIdToRemove); err != nil {
+		return err
 	}
 	if cmhResult := <-a.Srv.Store.ChannelMemberHistory().LogLeaveEvent(userIdToRemove, channel.Id, model.GetMillis()); cmhResult.Err != nil {
 		return cmhResult.Err

app/team.go

@@ -840,8 +840,8 @@ func (a *App) LeaveTeam(team *model.Team, user *model.User, requestorId string)
 	for _, channel := range *channelList {
 		if !channel.IsGroupOrDirect() {
 			a.InvalidateCacheForChannelMembers(channel.Id)
-			if result := <-a.Srv.Store.Channel().RemoveMember(channel.Id, user.Id); result.Err != nil {
-				return result.Err
+			if err := a.Srv.Store.Channel().RemoveMember(channel.Id, user.Id); err != nil {
+				return err
 			}
 		}
 	}