Percy hasn't contributed anything useful in the entire time we've used it and just causes a lot of false-positive failures. Access control to the service has been painful (particularly following the org migration, where it simply doesn't work for some members of the team), and there's no one maintaining the integration. Let's rip it out.

Contributor Checklist

• Changelog Entry If this PR changes user-facing behavior, please generate and add a
  changelog entry using the make cl command.
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  Please also consider whether the change requires notes within the upgrade
  guide. If you would like help with the docs, tag the nomad-docs team in this PR.

Reviewer Checklist

• Backport Labels Please add the correct backport labels as described by the internal
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• If a change needs to be reverted, we will roll out an update to the code within 7 days.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.