Update alerta/alerta-web Docker tag to v8.5.0 (#33)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| alerta/alerta-web | final | minor | `8.4.1` -> `8.5.0` |

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### Configuration

📅 **Schedule**: 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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 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box.

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This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).

Reviewed-on: #33
Co-authored-by: renovate-bot <bot@walbeck.it>
Co-committed-by: renovate-bot <bot@walbeck.it>

Dockerfile

@@ -1,4 +1,4 @@
-FROM alerta/alerta-web:8.4.1@sha256:450042a5c24e5782ff8ee0f144272815fedee7d83857be264e0156bac2624baa
+FROM alerta/alerta-web:8.5.0@sha256:ff659eee5889a676de01e926a5a0504532b7bee17b5dd4ee304186e704467e55
 
 RUN /venv/bin/pip install \
     git+https://git.walbeck.it/walbeck-it/matrix-alerta.git