Remove imports from Traffic Router source files that were never used

[ocket8888]

This just removes some imports that were never used from some Java files.

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Which Traffic Control components are affected by this PR?

• Traffic Router

What is the best way to verify this PR?

Make sure all existing tests still pass. If anything was actually needed I'd expect compilation to fail.

PR submission checklist

• [x] This PR utilizes existing tests
• [x] This PR doesn't need documentation
• [x] This PR doesn't need a CHANGELOG.md entry
• [x] This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY