Edit pass on 'Generate OpenAPI documents'

[guardrex]

Fixes #36143

While working on #36071, I noticed that the article could use a quick edit pass to conform to our styles.

WRT the two links in the reference link list ...

[OpenAPI version 3.1]: https://spec.openapis.org/oas/v3.1.1.html
[JSON Schema draft 2020-12]: https://json-schema.org/specification-links#2020-12

The first one was only used twice, which I cut down to one use by changing the following line later in the article ...

- By default, OpenAPI document generation creates a document that is compliant with [OpenAPI version 3.1](https://spec.openapis.org/oas/v3.1.1.html).
+ By default, OpenAPI document generation creates a document that is compliant with the OpenAPI specification.

... which should work just as well. The second link was only used once. Therefore, I was able to kill 🔪 the barely-used ref link list.

Otherwise, this is just our standard set of conventions ....... Scott Addie Days!™ conventions! 😆 I didn't adopt the usual uppercase placeholder names. I stuck with the article's use of mixed-case placeholders. However, I did convert everything over to braces {...} around them. If you think we should go with uppercase placeholder names, let me know. 👂

If there are concerns or confusion ... or death threats! 💀😨😆 ... over the updates, I'm 👂 for discussion and possible reversion.

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Internal previews

📄 File	🔗 Preview link
aspnetcore/fundamentals/openapi/aspnetcore-openapi.md	aspnetcore/fundamentals/openapi/aspnetcore-openapi

[Copilot]

Pull Request Overview

This PR performs an editorial pass on the ASP.NET Core OpenAPI documentation to improve consistency, clarity, and adherence to style guidelines. The changes focus on standardizing formatting conventions, improving readability, and ensuring proper cross-references are used throughout the document.

Key changes include:

• Standardized cross-references using <xref:> syntax instead of markdown links for API documentation
• Improved placeholder formatting using braces {...} convention
• Enhanced readability through better punctuation and formatting

[wadepickett]

Great set of improvements @guardrex. Looks good.