Removed minimum-stability: beta suggestion

Suggesting `minimum-stability: beta` sounds like a bad practice, as it will affect all of the other packages. `1.0@beta` should be safer, and do the same thing.

extensions/symfony-bundle.rst

@@ -38,19 +38,7 @@ following command in a terminal:
 
 .. code-block:: text
 
-    $ composer require "puli/symfony-bundle:~1.0"
-
-.. note::
-
-    Make sure that the "minimum-stability" setting is set to "beta" in
-    composer.json, otherwise the installation will fail:
-
-    .. code-block:: json
-
-        {
-            ...,
-            "minimum-stability": "beta"
-        }
+    $ composer require "puli/symfony-bundle:~1.0@beta"
 
 This will download the bundle to your project.