chore: remove walrus generate-sui-wallet

[wbbradley]

Description

Remove the generate-sui-wallet command.

Test plan

CI Pipeline.

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Release notes

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• Storage node:
• Aggregator:
• Publisher:
• CLI: Remove support for the walrus generate-sui-wallet ... command. This command was useful for early testing however it is now a distraction and its role can be filled by normal sui CLI tooling.

[github-actions]

Warning: This PR modifies the Walrus CLI. Please consider the following:

• Make sure the changes are backwards compatible. Consider deprecating options before
  removing them.
• Generally only use long CLI options, not short ones to avoid conflicts in the
  future.
• If you added new options or features, or modified the behavior, please document the
  changes in the release notes of the PR and update the documentation in the docs/book
  directory.

[github-actions]

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[mlegner]

Unless the command is actually non-functional and cannot be fixed easily, I'd probably keep it, even though we don't advertise it. It's possible some users actually use it in some scripts, and we can avoid breaking those. 🤷