Remove support of laravel 7

bump composer deps

composer.json

@@ -15,15 +15,13 @@
         "Sitemap"
     ],
     "require": {
-        "illuminate/support": "~7|~8",
-        "laravel/framework": "~7|~8",
-        "spatie/laravel-sitemap": "^5.8",
-        "kwaadpepper/enum": "^2.0"
+        "illuminate/support": "~8",
+        "laravel/framework": "~8",
+        "kwaadpepper/enum": "~2",
+        "spatie/laravel-sitemap": "^5.8"
     },
     "require-dev": {
-        "phpunit/phpunit": "~9.0",
-        "squizlabs/php_codesniffer": "^3.5",
-        "orchestra/testbench": "^6.13"
+        "slevomat/coding-standard": "^7.2"
     },
     "autoload": {
         "psr-4": {
@@ -41,5 +39,10 @@
                 "Kwaadpepper\\RefreshSitemap\\RefreshSitemapServiceProvider"
             ]
         }
+    },
+    "config": {
+        "allow-plugins": {
+            "dealerdirect/phpcodesniffer-composer-installer": true
+        }
     }
 }