[Tooling] SwiftLint: Use linter agent instead of default agent

[spencertransier]

Description

This PR updates the SwiftLint CI task to use the linter agent for running SwiftLint instead of the default agent.

Testing Details

This is good to go as long as CI (and especially SwiftLint) is green

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• Please check here if your pull request includes additional test coverage.
• I have considered if this change warrants release notes and have added them to the appropriate section in the CHANGELOG.md if necessary.

[mokagio]

Thanks!