cli: vulnerability alias to vulnerability list

[lucasmoura]

Why is this needed?

Running pro vulnerability is now an alias for running pro vulnerability list

Test Steps

Check that pro vulnerability works the same way as pro vulnerability list

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• (un)check this to re-run the checklist action

[github-actions]

PR Checklist

How to use this checklist

How to use this checklist

PR Author

For each section, check a box when it is true.
Uncheck a box if it becomes un-true.
Then check the box at the bottom of the PR description to re-run the action that creates this checklist.
The action that creates and updates this comment will retain your edits.
The action will fail if the checklist is not completed.

PR Reviewer

Check that the PR checklist action did not fail.
Double check that the author filled out the checklist accurately.
If you disagree with a checklist item, start a conversation.
For example, the author may say they don't think integration tests are necessary, but you may disagree.

Bug References

None.

Confirm

• I've properly referenced all bugs that this PR fixes

How to properly reference fixed bugs

• If this PR is related to a Jira item, include an SC-1234 reference in the PR title
• If this PR is fixes a GitHub issue, include a Fixes: #1234 reference in the commit that fixes the issue
• If this PR is fixes a Launchpad bug, include a LP: #12345678 reference in the commit that fixes the issue

Test Updates

Unit Tests

• I have updated or added any unit tests accordingly
• No unit test changes are necessary for this change

Integration Tests

• I have updated or added any integration tests accordingly
• No integration test changes are necessary for this change

Documentation

• Changes here need to be documented and I have referenced the docs PR in the description
• No documentation updates are necessary for this change

Does this PR require review from someone outside the core ubuntu-pro-client team?

• Yes, and I have requested those reviews via GitHub
• No