tests: Rename invalid json files to txt

Same as was done in 5f2584b648

Bug: T391586
Follows-Up: I966cddb337c9373ed3a369496548a8d8c538ae84
Change-Id: I757eb043f8043d6620fb69bd072d9bb9e97ad163
(cherry picked from commit 7a84c34398639d3422f81ab9711539c34d435621)

tests/phpunit/unit/tests/JsonSchemaAssertionTraitTest.php

@@ -31,7 +31,9 @@ class JsonSchemaAssertionTraitTest extends MediaWikiUnitTestCase {
 
 	public static function provideInvalidJson() {
 		$dir = __DIR__ . '/json';
-		foreach ( glob( __DIR__ . '/json/invalid*.json' ) as $file ) {
+		// T391586 - Malformed JSON doesn't pass linting while making releases, so
+		// to have a txt file extension.
+		foreach ( glob( __DIR__ . '/json/invalid*.{txt,json}' ) as $file ) {
 			yield $file => [ $file, "$dir/schema1.json" ];
 		}
 	}