Bump PHP version to 7.3

Author: barryvdh

composer.json

@@ -34,7 +34,7 @@
         }
     },
     "require": {
-        "php": "^7.2|^8",
+        "php": "^7.3|^8",
         "omnipay/common": "~3.0"
     },
     "require-dev": {
@@ -44,7 +44,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "3.0.x-dev"
+            "dev-master": "3.3.x-dev"
         }
     },
     "scripts": {