Update composer.json

Author: barryvdh

composer.json

@@ -23,18 +23,19 @@
         "psr-4": { "Omnipay\\Tests\\" : "src/" }
     },
     "require": {
+        "php": "^7.3|^8",
         "php-http/mock-client": "^1.1",
         "guzzlehttp/psr7": "^1",
         "mockery/mockery": "^1",
-        "phpunit/phpunit": "^5.7|^6"
+        "phpunit/phpunit": "^9"
     },
     "require-dev": {
         "omnipay/common": "^3",
-        "symfony/http-foundation": "^3|^4"
+        "symfony/http-foundation": "^3|^4|^5"
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "3.1.x-dev"
+            "dev-master": "4.0.x-dev"
         }
     },
     "prefer-stable": true