Update apps/updatenotification/lib/UpdateChecker.php

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

Author: susnux

apps/updatenotification/lib/UpdateChecker.php

@@ -57,7 +57,7 @@ public function getUpdateState(): array {
 	/**
 	 * Provide update information as initial state
 	 */
-	public function setInitialState() {
+	public function setInitialState(): void {
 		$updateState = $this->getUpdateState();
 		if (empty($updateState)) {
 			return;