[BUG] Json, CodecFormat.Json in endpoint type results in oneOf in yaml

Tapir version: 0.20.0-M3

Code to reproduce:

 val personEndpoint = endpoint.get
      .in(header[String]("Test").description("Test token").deprecated())
      .out(webSocketBody[String, CodecFormat.TextPlain, Json, CodecFormat.Json](AkkaStreams))

    val yaml = AsyncAPIInterpreter().toAsyncAPI(personEndpoint, "Header flags", "1.0").toYaml

should result in output yaml containing following lines .

'oneOf:':
      payload: {}
      contentType: application/json

Unfortunately such behavior is not correct.

Start with the provided personEndpoint reproduction, especially webSocketBodyString, CodecFormat.TextPlain, Json, CodecFormat.Json, and trace AsyncAPIInterpreter().toAsyncAPI(...).toYaml. Compare the generated YAML with the expected payload and ensure the JSON codec does not produce an incorrect oneOf structure.