move users service to app directory (#18257)

app/import_functions.go

@@ -17,8 +17,8 @@ import (
 	"strings"
 
 	"github.com/mattermost/mattermost-server/v6/app/request"
+	"github.com/mattermost/mattermost-server/v6/app/users"
 	"github.com/mattermost/mattermost-server/v6/model"
-	"github.com/mattermost/mattermost-server/v6/services/users"
 	"github.com/mattermost/mattermost-server/v6/shared/mlog"
 	"github.com/mattermost/mattermost-server/v6/store"
 	"github.com/mattermost/mattermost-server/v6/utils"