chore(deps): update dependency polyfill to 9.20.0

[thomhurst]

This PR contains the following updates:

Package	Type	Update	Change
Polyfill	nuget	minor	9.18.0 → 9.20.0

---

Release Notes

SimonCropp/Polyfill (Polyfill)

v9.20.0

Compare Source

---

Configuration

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

🚦 Automerge: Enabled.

♻ Rebasing: Whenever PR is behind base branch, or you tick the rebase/retry checkbox.

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

---

• If you want to rebase/retry this PR, check this box

---

This PR has been generated by Renovate Bot.

[claude]

Code Review

This is a routine dependency update bumping the Polyfill package from 9.18.0 → 9.20.0.

Change: Single-line version bump in TUnit.Core/TUnit.Core.targets.

Assessment

This is a straightforward, low-risk minor version update with no structural changes required. The Polyfill library provides compile-time type generation for older target frameworks (netstandard2.0, netstandard2.1, .NETFramework), and a minor bump here is unlikely to introduce breaking changes.

The change is correctly scoped — only the pinned version property _TUnitPolyfillVersion is updated, which is then conditionally applied based on the target framework. This is the right approach for managing this kind of transitive dependency.

No issues found. Auto-merge is enabled and appropriate for this type of routine dependency update.