3.0.4: rephrase now-outdated statement on minor spec version compatibility

[ralfhandl]

Section Versions claims

Each new minor version of the OpenAPI Specification SHALL allow any OpenAPI document that is valid against any previous minor version of the Specification, within the same major version, to be updated to the new Specification version with equivalent semantics. Such an update MUST only require changing the openapi property to the new minor version.

For example, a valid OpenAPI 3.0.2 document, upon changing its openapi property to 3.1.0, SHALL be a valid OpenAPI 3.1.0 document, semantically equivalent to the original OpenAPI 3.0.2 document. New minor versions of the OpenAPI Specification MUST be written to ensure this form of backward compatibility.

Now 3.1.0 is out, uses a different JSON Schema draft, and this statement does not reflect reality.

The first paragraph in this section explicitly allows correcting errors in the specification document with a patch version:

Typically, .patch versions address errors in this document, not the feature set.

So the two now erroneous paragraphs could simply be removed.

[ralfhandl]

@MikeRalphson could you please add the 3.0.4 label?

[MikeRalphson]

@ralfhandl would you be interested in an official OAI triage team hat? It would allow you to label and close issues.

[ralfhandl]

@MikeRalphson I would not object to that honor 😄