chore(deps): update dependency phoenix_live_dashboard to ~> 0.8

[renovate]

This PR contains the following updates:

Package	Update	Change
phoenix_live_dashboard	minor	~> 0.4 -> ~> 0.8

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

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[renovate]

⚠ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

♻ Renovate will retry this branch, including artifacts, only when one of the following happens:

• any of the package files in this branch needs updating, or
• the branch becomes conflicted, or
• you click the rebase/retry checkbox if found above, or
• you rename this PR's title to start with "rebase!" to trigger it manually

The artifact failure details are included below:

File name: mix.lock

Command failed: mix deps.update phoenix_live_dashboard
warning: use Mix.Config is deprecated. Use the Config module instead
  config/config.exs:8

warning: use Mix.Config is deprecated. Use the Config module instead
  config/dev.exs:1

** (Mix) Hex dependency resolution failed