fix: lower threshold for system address book sync

- Switch back to countUsers to have the actual value. countSeenUsers is bad if Nextcloud is connected to a larger directory, but only a part is using Nextcloud and therefore the seen count is much lower because the sync is done for all users.
- Lower the threshold to 100 for smaller installations.

Signed-off-by: Daniel Kesselberg <mail@danielkesselberg.de>

apps/dav/lib/Migration/Version1027Date20230504122946.php

@@ -49,7 +49,7 @@ public function __construct(private SyncService $syncService,
 	 * @param array $options
 	 */
 	public function postSchemaChange(IOutput $output, Closure $schemaClosure, array $options): void {
-		if($this->userManager->countSeenUsers() > 1000) {
+		if(array_sum($this->userManager->countUsers()) > 100) {
 			$this->config->setAppValue('dav', 'needs_system_address_book_sync', 'yes');
 			$output->info('Could not sync system address books during update - too many user records have been found. Please call occ dav:sync-system-addressbook manually.');
 			return;