minor #4955 Fixed wrong API link (dosten)

This PR was merged into the 2.3 branch.

Discussion
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Fixed wrong API link

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all since 2.3
| Fixed tickets | -

The `makeDisposition` method is in the `ResponseHeaderBag` class, not in the `Response` class.

Commits
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543bc30 Update introduction.rst

Author: wouterj

components/http_foundation/introduction.rst

@@ -439,7 +439,7 @@ Serving Files
 When sending a file, you must add a ``Content-Disposition`` header to your
 response. While creating this header for basic file downloads is easy, using
 non-ASCII filenames is more involving. The
-:method:`Symfony\\Component\\HttpFoundation\\Response::makeDisposition`
+:method:`Symfony\\Component\\HttpFoundation\\ResponseHeaderBag::makeDisposition`
 abstracts the hard work behind a simple API::
 
     use Symfony\Component\HttpFoundation\ResponseHeaderBag;