Drop support for PHP 8.1.

Author: prwater

.github/workflows/unit.yml

@@ -16,7 +16,6 @@ jobs:
       fail-fast: false
       matrix:
         php-version:
-          - "8.1"
           - "8.2"
           - "8.3"
           - "8.4"

composer.json

@@ -9,7 +9,7 @@
   ],
   "license": "MIT",
   "require": {
-    "php": ">=8.1",
+    "php": ">=8.2",
     "setbased/exception": "^2.3.0"
   },
   "minimum-stability": "dev",