chore: drop PHP 5.x, PHPUnit 5.x and PHPUnit polyfill (#15)

Author: keradus

.github/workflows/ci.yaml

@@ -28,9 +28,8 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - php-version: '5.6'
-            composer-flags: '--prefer-stable --prefer-lowest'
           - php-version: '7.0'
+            composer-flags: '--prefer-stable --prefer-lowest'
           - php-version: '7.1'
           - php-version: '7.2'
           - php-version: '7.3'

composer.json

@@ -10,9 +10,8 @@
         }
     ],
     "require": {
-        "php": "^5.5 || ^7.0 || ^8.0",
-        "phpunit/phpunit": "^5.7.27 || ^6.5.14 || ^7.5.20 || ^8.0 || ^9.0 || ^10.0",
-        "phpunitgoodpractices/polyfill": "^1.4"
+        "php": "^7.0 || ^8.0",
+        "phpunit/phpunit": "^6.5.14 || ^7.5.20 || ^8.0 || ^9.0 || ^10.0"
     },
     "autoload": {
         "psr-4": {