Fixing tests

Most were a case of adding void return statement to setUp and tearDown,
also needed to add 6th `null` param to indieauth method. Its for
code_verifier, issue created to work out what I should actually be doing
with that.

tests/Unit/Jobs/ProcessWebMentionJobTest.php

@@ -20,7 +20,7 @@ class ProcessWebMentionJobTest extends TestCase
 {
     use DatabaseTransactions;
 
-    public function tearDown()
+    protected function tearDown(): void
     {
         $fs = new FileSystem();
         if ($fs->exists(storage_path() . '/HTML/https')) {