[release/8.0] Update Microsoft.Extensions.Http.cs

[github-actions]

Backport of #90916 to release/8.0

Fixes #90911

/cc @CarnaViire @ShreyasJejurkar

Customer Impact

The new 8.0 API ConfigureHttpClientDefaults introduced in #87914 (PR #87953 merged on 7/14) was supposed to be extension method, but this was by accident omitted from ref (it was correctly part of implementation of the API).

Note: api-compat tool didn't catch the discrepancy, although it should have. We created a new issue dotnet/sdk#34824 to address it for future cases.

Testing

CI + manual inspection of ref assembly

Risk

Very low, this is a new feature introduced in 8.0

[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

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Issue Details

---

Backport of #90916 to release/8.0

/cc @CarnaViire @ShreyasJejurkar

Customer Impact

Testing

Risk

IMPORTANT: If this backport is for a servicing release, please verify that:

• The PR target branch is release/X.0-staging, not release/X.0.

• If the change touches code that ships in a NuGet package, you have added the necessary package authoring and gotten it explicitly reviewed.

Author:	github-actions[bot]
Assignees:	-
Labels:	new-api-needs-documentation, area-Extensions-HttpClientFactory
Milestone:	-

[karelz]

I am giving M2 approval -- this is a new 8.0 API, where ref is not correct, which makes it harder to use.
Fix is simple, low risk and was validated.

@carlossanlop do you need anything else from us?