minor #16154 Update symfony_server.rst (noniagriconomie)

This PR was merged into the 4.4 branch.

Discussion
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Update symfony_server.rst

Small PR related to https://www.php.net/supported-versions.php

Commits
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6b392f2 Update symfony_server.rst

Author: javiereguiluz

setup/symfony_server.rst

@@ -114,10 +114,10 @@ root directory:
     $ cd my-project/
 
     # use a specific PHP version
-    $ echo 7.2 > .php-version
+    $ echo 7.4 > .php-version
 
-    # use any PHP 7.x version available
-    $ echo 7 > .php-version
+    # use any PHP 8.x version available
+    $ echo 8 > .php-version
 
 .. tip::