[FLASK] Remove long-running Snap permission

[david0xd]

Description

This PR removes long-running Snap endowment/permission.

Snaps team have decided to remove this endowment because of its unpredictable security concerns around running Snaps indefinitely. This endowment is removed in favor of the new endowments that will be focused on solving certain use cases that require snap to be running for more time than default.

Related issues

Fixes #945

Related PR

MetaMask/snaps#1751 (required)
MetaMask/metamask-docs#919

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• I’ve followed MetaMask Coding Standards.
• I've clearly explained:
  • What problem this PR is solving.
  • How this problem was solved.
  • How reviewers can test my changes.
• I’ve indicated what issue this PR is linked to: Fixes #???
• I’ve included tests if applicable.
• I’ve documented any added code.
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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.

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