Fix incorrect PR link in signature-controller changelog

[jeffsmale90]

Explanation

#8478 incorrectly "fixed" the PR link in @metamask/signature-controller's changelog, where the link text and link url referred to different PR numbers.

This PR reverts and corrects the PR reference.

References

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Low Risk
Changelog-only edit; no runtime code or dependencies are changed.

Overview
Fixes an incorrect PR reference in @metamask/signature-controller’s changelog by updating the 23.0.0 entry for the breaking @metamask/keyring-controller peer dependency bump to point to the correct pull request.

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