Update dependencies, drop support for PHP < 8.0

Author: timoschinkel

composer.json

@@ -4,13 +4,13 @@
     "type": "library",
     "license": "MIT",
     "require": {
-        "php": "^7.2 || ^8.0",
+        "php": "^8.0",
         "psr/http-client": "^1.0",
         "psr/http-message": "^1.0"
     },
     "require-dev": {
-        "phpspec/prophecy": "^1.12",
-        "phpunit/phpunit": "^8.0 || ^9.0",
+        "phpspec/prophecy": "^1.17",
+        "phpunit/phpunit": "^9.0 || ^10.0",
         "squizlabs/php_codesniffer": "^3.5"
     },
     "autoload": {