chore(deps) Update mcr.microsoft.com/dotnet/sdk Docker tag to v9

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
mcr.microsoft.com/dotnet/sdk	image	major	8.0-alpine -> 9.0-alpine
mcr.microsoft.com/dotnet/sdk	final	major	8.0-alpine -> 9.0-alpine
mcr.microsoft.com/dotnet/sdk	stage	major	8.0-alpine -> 9.0-alpine

---

Configuration

📅 Schedule: Branch creation - "before 10pm on Sunday" in timezone America/Chicago, Automerge - At any time (no schedule defined).

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

♻ 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 these updates again.

---

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

---

This PR was generated by Mend Renovate. View the repository job log.