Issue #3121020 by dww, Kristen Pol: Move Update Manager XML test fixtures into...

Issue #3121020 by dww, Kristen Pol: Move Update Manager XML test fixtures into a fixtures/release-history directory

(cherry picked from commit 7255efdd)

core/modules/update/tests/modules/update_test/src/Controller/UpdateTestController.php

@@ -63,7 +63,7 @@ public function updateTest($project_name, $version) {
       $availability_scenario = '#broken#';
     }
 
-    $file = __DIR__ . "/../../$project_name.$availability_scenario.xml";
+    $file = __DIR__ . "/../../../../fixtures/release-history/$project_name.$availability_scenario.xml";
     $headers = ['Content-Type' => 'text/xml; charset=utf-8'];
     if (!is_file($file)) {
       // Return an empty response.