Merge pull request #3180 from api-platform/fix/problem-details-link-rfc

Update Problem Details link to point to RFC

Author: teohhanhui

README.md

@@ -4,7 +4,7 @@ API Platform Core is an easy to use and powerful system to create [hypermedia-dr
 It is a component of the [API Platform framework](https://api-platform.com) and it can be integrated
 with [the Symfony framework](https://symfony.com) using the bundle distributed with the library.
 
-It natively supports popular open formats including [JSON for Linked Data (JSON-LD)](https://json-ld.org), [Hydra Core Vocabulary](https://www.hydra-cg.com), [OpenAPI v2 (formerly Swagger) and v3](https://www.openapis.org), [HAL](https://tools.ietf.org/html/draft-kelly-json-hal-08) and [HTTP Problem](https://tools.ietf.org/html/draft-ietf-appsawg-http-problem-03).
+It natively supports popular open formats including [JSON for Linked Data (JSON-LD)](https://json-ld.org), [Hydra Core Vocabulary](https://www.hydra-cg.com), [OpenAPI v2 (formerly Swagger) and v3](https://www.openapis.org), [HAL](https://tools.ietf.org/html/draft-kelly-json-hal-08) and [Problem Details](https://tools.ietf.org/html/rfc7807).
 
 Build a working and fully-featured CRUD API in minutes. Leverage the awesome features of the tool to develop complex and
 high performance API-first projects. Extend or override everything you want.