feat: Deprecating the old API documentation (#1144)

Author: netmilk

sources/platform/api_v2/api_v2_reference.apib

@@ -1,7 +1,9 @@
 FORMAT: 1A
 HOST: https://api.apify.com/
 
-# Apify API
+# Apify API (This document is deprecated)
+
+>  UPDATE 2024-08-09: This documentation is no longer updated. Please refer to the [new Apify API documentation](https://docs.apify.com/api/v2).
 
 The Apify API (version 2) provides programmatic access to the [Apify platform](https://docs.apify.com).
 The API is organized around [RESTful](https://en.wikipedia.org/wiki/Representational_state_transfer)