Marcin Figiel

Adopt IANA standard for YAML Media Type

1

### Issue description Micronaut uses a [custom media type](https://github.com/micronaut-projects/micronaut-core/issues) for YAML: `application/x-yaml`, while IANA [recently registered](https://www.rfc-editor.org/rfc/rfc9512.html) an official `application/yaml`. Micronaut should adopt this official type in its codebase.