Update dependency MSTest.Sdk to 4.2.1

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
MSTest.Sdk	4.0.2 → 4.2.1

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Release Notes

microsoft/testfx (MSTest.Sdk)

v4.2.1

See the release notes here

v4.1.0

See the release notes here

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Configuration

📅 Schedule: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

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