Update openapi.yml to v3.1.0 fix deprecated fields

[0ex-d]

Update to latest spec and remove deprecated field (example -> examples)
For more information, please refer to this https://spec.openapis.org/oas/v3.1.0.html#example-object

Closes #1789

[0ex-d]

For the new spec, examples is an array that get's rendered as a dropdown of options, please advice if this is how the UI should appear.

CC: @peterjan @lukechampine

[peterjan]

@0ex-d I took a quick look at how we use examples and suggest we drop them where they no longer make sense in OpenAPI 3.1.0. We do need to ensure that when we remove an example, the schema still specifies the type and any patterns or constraints that the field must meet.

For instance, if an object has a field like blockheight, I sometimes specified example: 506412 to make the output less dull, as it would otherwise display blockheight: 0. It doesn't make sense to rewrite such examples into an examples object in 3.1.0. In such cases, you can remove the examples entirely.