Migrate Preference.DeleteCategory to Sync by default (#10927)

app/team.go

@@ -945,8 +945,8 @@ func (a *App) LeaveTeam(team *model.Team, user *model.User, requestorId string)
 	}
 
 	// delete the preferences that set the last channel used in the team and other team specific preferences
-	if result := <-a.Srv.Store.Preference().DeleteCategory(user.Id, team.Id); result.Err != nil {
-		return result.Err
+	if err := a.Srv.Store.Preference().DeleteCategory(user.Id, team.Id); err != nil {
+		return err
 	}
 
 	a.ClearSessionCacheForUser(user.Id)