Revert "PHP 8 requis"

This reverts commit 6ac46ccc.

CHANGELOG.md

 CHANGELOG
 =========
 
-3.0.0
------
-- PHP 8 requis
-
 2.0.0
 -----
 - SUppression de la dépendance avec unicaen/app

composer.json

@@ -8,7 +8,7 @@
         }
     ],
     "require": {
-        "php": "^8.0",
+        "php": "^7.3 || ^8.0",
         "webmozart/assert": "^1.11",
         "cboden/ratchet": "^0.4.4",
         "monolog/monolog": "^2.8",