minor #2524 [Turbo] Remove obselete Mercure configuration (docs) (smnandre)

This PR was squashed before being merged into the 2.x branch.

Discussion
----------

[Turbo] Remove obselete Mercure configuration (docs)

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes/no <!-- please update src/**/CHANGELOG.md files -->
| Issues        | Fix #2518
| License       | MIT

This PR replaces #2519 (that did not use current config format) and add the changes missing on the same page.

- [Update Mercure bundle documentation](ef688d4)
- [Fix Mercure controller configuration](f221d4d)
- [Remove obselete Mercure turbo/hub configuration](a8403c0)
- [Remove very old versionadded warning](c8dcb5e)
- [Remove Symfony 6.2+ comment](3a88f32)

Commits
-------

369f345 [Turbo] Remove obselete Mercure configuration (docs)

Author: smnandre

src/Turbo/doc/index.rst

@@ -342,11 +342,6 @@ clients. There are two main ways to receive the updates:
 Forms
 ^^^^^
 
-.. versionadded:: 2.1
-
-    Prior to 2.1, ``TurboStreamResponse::STREAM_FORMAT`` was used instead of ``TurboBundle::STREAM_FORMAT``.
-    Also, one had to return a new ``TurboStreamResponse()`` object as the third argument to ``$this->render()``.
-
 Let's discover how to use Turbo Streams to enhance your `Symfony forms`_::
 
     // src/Controller/TaskController.php
@@ -383,7 +378,6 @@ Let's discover how to use Turbo Streams to enhance your `Symfony forms`_::
                 return $this->redirectToRoute('task_success', [], Response::HTTP_SEE_OTHER);
             }
 
-            // Symfony 6.2+
             return $this->render('task/new.html.twig', [
                 'form' => $form,
             ]);
@@ -500,7 +494,7 @@ Then, enable the "mercure stream" controller in ``assets/controllers.json``:
         "mercure-turbo-stream": {
     +         "enabled": true,
     -         "enabled": false,
-            "fetch": "lazy"
+            "fetch": "eager"
         }
     },
 
@@ -512,14 +506,19 @@ If you use Symfony Flex, the configuration has been generated for you,
 be sure to update the ``MERCURE_URL`` in the ``.env`` file to point to a
 Mercure Hub (it's not necessary if you are using Symfony Docker).
 
-Otherwise, configure Mercure Hub(s) to use:
+Otherwise, configure Mercure Hub(s) as explained in the documentation:
 
 .. code-block:: yaml
 
-    # config/packages/turbo.yaml
-    turbo:
-        mercure:
-            hubs: [default]
+    # config/packages/mercure.yaml
+    mercure:
+        hubs:
+            default:
+                url: '%env(MERCURE_URL)%'
+                public_url: '%env(MERCURE_PUBLIC_URL)%'
+                jwt:
+                    secret: '%env(MERCURE_JWT_SECRET)%'
+                    publish: '*'
 
 Let's create our chat::
 
@@ -785,13 +784,6 @@ the following configuration:
                 url: https://hub2.example.net/.well-known/mercure
                 jwt: snip
 
-.. code-block:: yaml
-
-    # config/packages/turbo.yaml
-    turbo:
-        mercure:
-            hubs: [hub1, hub2]
-
 Use the appropriate Mercure ``HubInterface`` service to send a change
 using a specific transport::