fix: ensure jobId is a string

Signed-off-by: John Molakvoæ (skjnldsv) <skjnldsv@protonmail.com>

Author: skjnldsv

lib/private/BackgroundJob/JobRuns.php

@@ -69,7 +69,7 @@ public function runningJobs(int $limit = 200): \Generator {
 		foreach ($result->iterateAssociative() as $row) {
 			$snowflakeInfo = $this->snowflakeDecoder->decode((string)$row['run_id']);
 			yield new JobRun(
-				$row['run_id'],
+				(string) $row['run_id'],
 				$this->classesRegistry->getName($row['class_id']),
 				$snowflakeInfo->getServerId(),
 				$row['pid'],