minor symfony#6211 Remove 2.3.* from composer snippets in the form component doc (Nicofuma)

This PR was submitted for the master branch but it was merged into the 3.0 branch instead (closes symfony#6211).

Discussion
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Remove 2.3.* from composer snippets in the form component doc

Commits
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97ef850 Remove 2.3.* from composer snippets in the form component doc

Author: xabbuh

Diff for: components/form/introduction.rst

@@ -163,14 +163,14 @@ component offers a rich integration.
 
 To use the integration, you'll need the ``TwigBridge``, which provides integration
 between Twig and several Symfony components. If you're using Composer, you
-could install the latest 2.3 version by adding the following ``require``
+could install the latest 3.x version by adding the following ``require``
 line to your ``composer.json`` file:
 
 .. code-block:: json
 
     {
         "require": {
-            "symfony/twig-bridge": "2.3.*"
+            "symfony/twig-bridge": "~3.0"
         }
     }
 
@@ -243,15 +243,15 @@ via your own Twig extension.
 
 To use the built-in integration, be sure that your project has Symfony's
 Translation and :doc:`Config </components/config/introduction>` components
-installed. If you're using Composer, you could get the latest 2.3 version
+installed. If you're using Composer, you could get the latest 3.x version
 of each of these by adding the following to your ``composer.json`` file:
 
 .. code-block:: json
 
     {
         "require": {
-            "symfony/translation": "2.3.*",
-            "symfony/config": "2.3.*"
+            "symfony/translation": "~3.0",
+            "symfony/config": "~3.0"
         }
     }
 
@@ -295,13 +295,13 @@ array or object) and pass it through your own validation system.
 
 To use the integration with Symfony's Validator component, first make sure
 it's installed in your application. If you're using Composer and want to
-install the latest 2.3 version, add this to your ``composer.json``:
+install the latest 3.x version, add this to your ``composer.json``:
 
 .. code-block:: json
 
     {
         "require": {
-            "symfony/validator": "2.3.*"
+            "symfony/validator": "~3.0"
         }
     }