minor #747 Fix name of file inside the comments for BookFactory (harikt)

This PR was merged into the 1.11 branch.

Discussion
----------

| Q               | A
| --------------- | -----
| Bug fix?        | no
| New feature?    | no
| BC breaks?      | no
| Deprecations?   | no
| Related tickets | fixes parts of documentation.
| License         | MIT


Commits
-------

154a3d7 Fix name of file inside the comments for BookFactory

docs/resource_factories.md

@@ -21,7 +21,7 @@ It has a `createNew` method with no arguments.
 ## Define your custom factory
 
 ```php
-// src/Factory/BookRepository.php
+// src/Factory/BookFactory.php
 
 declare(strict_types=1);
 
@@ -54,7 +54,7 @@ services:
 ## Use your custom method
 
 ```php
-// src/Factory/BookRepository.php
+// src/Factory/BookFactory.php
 
 declare(strict_types=1);
 
@@ -123,7 +123,7 @@ You can pass arguments to your factory method.
 It uses the [Symfony expression language](https://symfony.com/doc/current/components/expression_language.html) component.
 
 ```php
-// src/Factory/BookRepository.php
+// src/Factory/BookFactory.php
 
 declare(strict_types=1);
 
@@ -213,7 +213,7 @@ class Book implements ResourceInterface
 ## Use a callable for your custom factory
 
 ```php
-// src/Factory/BookRepository.php
+// src/Factory/BookFactory.php
 
 declare(strict_types=1);