fix: Update help center URLs

[wtzb]

Description

The MetaMask help center has migrated from using Zendesk to Docusaurus. The old Zendesk URL is no longer in use, and the support.metamask.io domain should be used instead.

Old support links still using metamask.zendesk.com will no longer function as of this week, so I've replaced these with the correct, modern URLs. Links following the old Zendesk format (support.metamask.io/hc/en-us/...) have also been replaced with the modern versions.

Also see MetaMask/metamask-extension#24286.

Related issues

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Manual testing steps

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Screenshots/Recordings

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Before

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After

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Pre-merge author checklist

• [*] I’ve followed MetaMask Contributor Docs and MetaMask Mobile 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.

[wtzb]

I have read the CLA Document and I hereby sign the CLA.

[sethkfman]

LGTM

[metamaskbot]

No release label on PR. Adding release label release-7.24.3 on PR, as PR was cherry-picked in branch 7.24.3.