Use semver for API version in example

[dragetd]

The specification recommends using semver for version specifications here: https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.1.md#versions

[MikeRalphson]

This does seem to be the only instance of a non-semver version property value across the examples directory and the spec itself, so this LGTM. Many thanks for the PR!

[MikeRalphson]

TSC Happy to make this change to follow our own best practices, rather than to signal an implicit mandate to use semver here.

[earth2marsh]

Consider adding a # this represents the version of the specification document. While semver is recommended, any string is acceptable.

[MikeRalphson]

@earth2marsh I'd be happy to see such an informative comment in at least one of the examples.

[dragetd]

IMHO there is a spec, which should (and does) specify what is allowed, what not and what is recommended / best pratice. And example are just examples. It is nice if they follow those best practice.

I would also be okay with just reverting the PR than adding comment noise, but that is not my beer.

I like my bike-shed green. :)