Set minimum PHP version to 7.2.5

Author: mbabker

composer.json

@@ -6,7 +6,7 @@
     "homepage": "https://github.com/joomla-framework/github-api",
     "license": "GPL-2.0-or-later",
     "require": {
-        "php": "~7.2",
+        "php": "^7.2.5",
         "joomla/http": "~1.3|~2.0",
         "joomla/registry": "^1.4.5|~2.0",
         "joomla/uri": "~1.0|~2.0"