do not use outdated PHP version. refs #968 (#976)

src/Packagist/WebBundle/Resources/views/Web/index.html.twig

@@ -43,7 +43,7 @@
     "name": "your-vendor-name/package-name",
     "description": "A short description of what your package does",
     "require": {
-        "php": "^5.6.37 || ^7.0",
+        "php": "^7.2",
         "another-vendor/package": "1.*"
     }
 }</code></pre>