Update leakcanary to v3.0-alpha-8

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
com.squareup.leakcanary:leakcanary-object-watcher-android	3.0-alpha-7 -> 3.0-alpha-8
com.squareup.leakcanary:shark	3.0-alpha-7 -> 3.0-alpha-8
com.squareup.leakcanary:leakcanary-android	3.0-alpha-7 -> 3.0-alpha-8

---

Release Notes

square/leakcanary (com.squareup.leakcanary:leakcanary-object-watcher-android)

### [`v3.0-alpha-8`](https://togithub.com/square/leakcanary/releases/tag/v3.0-alpha-8) See [Change Log](https://square.github.io/leakcanary/changelog)

---

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 these updates again.

---

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

---

This PR has been generated by Mend Renovate. View repository job log here.