Fix namespace/filepath mismatches found by DOCtor-RST

- Fix BlogPostReviewSubscriber filepath from src/App/EventSubscriber to src/EventSubscriber
- Fix BlogPostPublishSubscriber filepath from src/App/EventSubscriber to src/EventSubscriber
- Fix Foo namespace from Foo to App\Foo to match src/Foo filepath

Author: OskarStark

contributing/documentation/standards.rst

@@ -101,7 +101,7 @@ Example
 .. code-block:: php
 
     // src/Foo/Bar.php
-    namespace Foo;
+    namespace App\Foo;
 
     use Acme\Demo\Cat;
     // ...

workflow.rst

@@ -666,7 +666,7 @@ list of the guard event names.
 This example stops any blog post being transitioned to "reviewed" if it is
 missing a title::
 
-    // src/App/EventSubscriber/BlogPostReviewSubscriber.php
+    // src/EventSubscriber/BlogPostReviewSubscriber.php
     namespace App\EventSubscriber;
 
     use App\Entity\BlogPost;
@@ -958,7 +958,7 @@ This example has been simplified; in production you may prefer to use the
 :doc:`Translation </translation>` component to manage messages in one
 place::
 
-    // src/App/EventSubscriber/BlogPostPublishSubscriber.php
+    // src/EventSubscriber/BlogPostPublishSubscriber.php
     namespace App\EventSubscriber;
 
     use Symfony\Component\EventDispatcher\EventSubscriberInterface;