Update ThemingControllerTest.php

Fixed tests for https://github.com/nextcloud/server/pull/8633

apps/theming/tests/Controller/ThemingControllerTest.php

@@ -526,7 +526,7 @@ class ThemingControllerTest extends TestCase {
 		return [
 			[UPLOAD_ERR_INI_SIZE, 'The uploaded file exceeds the upload_max_filesize directive in php.ini'],
 			[UPLOAD_ERR_FORM_SIZE, 'The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form'],
-			[UPLOAD_ERR_PARTIAL, 'The uploaded file was only partially uploaded'],
+			[UPLOAD_ERR_PARTIAL, 'The file was only partially uploaded'],
 			[UPLOAD_ERR_NO_FILE, 'No file was uploaded'],
 			[UPLOAD_ERR_NO_TMP_DIR, 'Missing a temporary folder'],
 			[UPLOAD_ERR_CANT_WRITE, 'Failed to write file to disk.'],