fix: Remove UnconnectedAlert component and state

[darkwing]

Description

The new Multichain component removed the old UnconnectedAlert component usage; this PR removes the file and state involved.

Related issues

Fixes: N/A

Manual testing steps

N/A, just removes old component.

Screenshots/Recordings

Before

N/A

After

N/A

Pre-merge author checklist

• I’ve followed MetaMask Coding Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

[github-actions]

CLA Signature Action: All authors have signed the CLA. You may need to manually re-run the blocking PR check if it doesn't pass in a few minutes.

[EtherWizard33]

I looked into the lint error that came up in the checks above.
I ran the repo from github codespaces, and yarn lint.
It's simply the removed component that needs to be removed from the duck file.
Here is a screenshot of the change i did to fix the lint.

[metamaskbot]

Builds ready [489fdd9]

• builds: chrome, firefox
• builds (beta): chrome
• builds (flask): chrome, firefox
• builds (MMI): chrome, firefox
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Background Module Init Stats
• mv3: UI Init Stats
• mv3: Module Load Stats
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• code coverage: Report
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5, 6
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8
  • content-script: 0
  • ui: 0, 1, 10, 2, 3, 4, 5, 6, 7, 8, 9

Page Load Metrics (1286 ± 589 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	60	168	99	26	13
		domContentLoaded	10	46	19	10	5
		load	50	2945	1286	1227	589
		domInteractive	9	46	19	10	5

Bundle size diffs [🚀 Bundle size reduced!]

• background: 943 Bytes (0.03%)
• ui: 76 Bytes (0.00%)
• common: -4.64 KiB (-0.08%)