chore(ci): fix wrong type annotations

Signed-off-by: grnd-alt <git@belakkaf.net>

Author: grnd-alt

lib/Service/FileService.php

@@ -83,7 +83,7 @@ public function extendData(Attachment $attachment) {
 	}
 
 	/**
-	 * @return array
+	 * @return array|null
 	 * @throws StatusException
 	 */
 	private function getUploadedFile() {

lib/Service/FilesAppService.php

@@ -332,7 +332,7 @@ public function createFromImport(Attachment $attachment, string $content): Attac
 	}
 
 	/**
-	 * @return array
+	 * @return array|null
 	 * @throws StatusException
 	 */
 	private function getUploadedFile() {

lib/Service/PermissionService.php

@@ -303,7 +303,7 @@ public function findUsers($boardId, $refresh = false) {
 					continue;
 				}
 				foreach ($group->getUsers() as $user) {
-					$users[(string)$user->getUID()] = new User($user->getUID(), $this->userManager);
+					$users[$user->getUID()] = new User($user->getUID(), $this->userManager);
 				}
 			}