build(deps): drop PHP 7.x for incompatiblity

Signed-off-by: Arthur Schiwon <blizzz@arthur-schiwon.de>

Author: blizzz

composer.json

@@ -3,7 +3,7 @@
     "description": "Nextcloud coding standards for the php cs fixer",
     "type": "library",
     "require": {
-        "php": "^7.3|^8.0",
+        "php": "^8.0",
         "php-cs-fixer/shim": "^3.17",
         "kubawerlos/php-cs-fixer-custom-fixers": "^3.22"
     },