Update PHP version requirement in composer.json to 8.3 and adjust CI workflow to only test against PHP 8.3

Author: dgtlss

.github/workflows/ci.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php: [ '8.1', '8.2', '8.3' ]
+        php: [ '8.3' ]
 
     steps:
       - name: Checkout

composer.json

@@ -8,7 +8,7 @@
     { "name": "Nathan Langer", "email": "nathanlanger@googlemail.com" }
   ],
   "require": {
-    "php": ">=8.1"
+    "php": ">=8.3"
   },
   "require-dev": {
     "phpunit/phpunit": "^10.5",