Modified updateUserNotifyProps to directly update the field (#18097)

* Modified updateUserNotifyProps to directly update the field

The method was only being used during import and it unnecessarily
made multiple queries to the DB.

Changed to a separate query that just updated the props field.

https://community-daily.mattermost.com/plugins/focalboard/workspace/zyoahc9uapdn3xdptac6jb69ic?id=285b80a3-257d-41f6-8cf4-ed80ca9d92e5&v=495cdb4d-c13a-4992-8eb9-80cfee2819a4&c=e4f9a891-85d6-4886-8590-1e327f7f8b8f

```release-note
NONE
```

* invalidating cache

```release-note
NONE
```

services/users/users.go

@@ -193,6 +193,10 @@ func (us *UserService) UpdateUser(user *model.User, allowRoleUpdate bool) (*mode
 	return us.store.Update(user, allowRoleUpdate)
 }
 
+func (us *UserService) UpdateUserNotifyProps(userID string, props map[string]string) error {
+	return us.store.UpdateNotifyProps(userID, props)
+}
+
 func (us *UserService) DeactivateAllGuests() ([]string, error) {
 	users, err := us.store.DeactivateGuests()
 	if err != nil {