Fix min Android version in package.json

Author: aurimasc

com.unity.mobile.notifications/package.json

@@ -3,7 +3,7 @@
   "displayName": "Mobile Notifications",
   "version": "2.0.1",
   "unity": "2019.4",
-  "description": "Mobile Notifications package adds support for scheduling local repeatable or one-time notifications on iOS and Android.\n\nRequires iOS 10 and Android 4.4 or above.",
+  "description": "Mobile Notifications package adds support for scheduling local repeatable or one-time notifications on iOS and Android.\n\nRequires iOS 10 and Android 5.1 or above.",
   "keywords": [
     "Android",
     "iOS",