Prefer xref over code-style

[mikekistler]

This PR converts code-style references to .NET classes to xref references.

Prior to this there was a mix of code-style and xref references in this file.

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Internal previews

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

[tdykstra]

Looks good, I mention one optional format.

[mikekistler]

@tdykstra @captainsafia I've switched the links to use a style like Tom suggested, but I had added one more stylistic twist. In cases where the link was to an attribute and was followed by "attribute", I moved "attribute" inside the link text. Likewise for "extension method". Here's a snip that shows how this looks now:

I don't have strong feelings about this but it seems worth trying. Let me know if you like it better the other way and I can easily change it.

[tdykstra]

I don't have strong feelings about this but it seems worth trying.

I don't either, so I'd be interested in getting input from @captainsafia and @Rick-Anderson

[mikekistler]

@captainsafia convinced me that we should not put "attribute" or "extension method" inside the link text, so I just pushed another commit that reverts that stylistic twist.

I think this is good to go now. @captainsafia can you please give it a quick review & approval and then I will merge.

[guardrex]

@mikekistler ... Please squash your PRs when merging.

[mikekistler]

@guardrex Apologies -- I will try to remember to do this next time.

[guardrex]

No worries ... just keeping the history tidy 😄 .