fix: wrong merged mime type

Author: vinceAmstoutz

core/content-negotiation.md

@@ -24,7 +24,7 @@ Available formats are:
 | [GraphQL](graphql.md)                                 | n/a         | n/a                           | yes                               |
 | [JSON:API](https://jsonapi.org/)                      | `jsonapi`   | `application/vnd.api+json`    | yes                               |
 | [HAL](https://stateless.group/hal_specification.html) | `jsonhal`   | `application/hal+json`        | yes                               |
-| [YAML](https://yaml.org/)                             | `yaml`      | `application/x-yaml`          | no                                |
+| [YAML](https://yaml.org/)                             | `yaml`      | `application/yaml`          | no                                |
 | [CSV](https://tools.ietf.org/html/rfc4180)            | `csv`       | `text/csv`                    | no                                |
 | [HTML](https://whatwg.org/) (API docs)                | `html`      | `text/html`                   | no                                |
 | [XML](https://www.w3.org/XML/)                        | `xml`       | `application/xml`, `text/xml` | no                                |