Support PHP 7.1, acknowledging tests will not run

Unfortunately dms/phpunit-arraysubset-asserts does not support older
versions of PHPUnit, so for now it's not possible to run tests on PHP
7.1 and 7.2. See dms/phpunit-arraysubset-asserts#11

.github/workflows/php.yml

@@ -13,7 +13,7 @@ jobs:
     
     strategy:
       matrix:
-        php-versions: ['7.2', '7.3', '7.4', '8.0']
+        php-versions: ['7.3', '7.4', '8.0']
 
     steps:
     - uses: actions/checkout@v2

composer.json

@@ -2,7 +2,7 @@
     "name": "tobyz/json-api-server",
     "description": "A fully automated JSON:API server implementation in PHP.",
     "require": {
-        "php": "^7.2|^8.0",
+        "php": ">=7.1",
         "doctrine/inflector": "^1.3",
         "json-api-php/json-api": "^2.2",
         "nyholm/psr7": "^1.3",
@@ -31,10 +31,9 @@
         }
     },
     "require-dev": {
-        "dms/phpunit-arraysubset-asserts": "^0.2",
-        "helmich/phpunit-json-assert": "^3.0",
+        "dms/phpunit-arraysubset-asserts": "^0.2.1",
         "phpspec/prophecy-phpunit": "^2.0",
-        "phpunit/phpunit": "^9.0"
+        "phpunit/phpunit": "^9.4"
     },
     "scripts": {
         "test": "phpunit"