Use EPEL trafficserver RPM for CodeQL.

[zrhoffman]

This PR gets the CodeQL C++ workflow working again by using the EPEL trafficserver RPM instead of an outdated COPR RPM that preceded trafficserver returning tp EPEL.

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Which Traffic Control components are affected by this PR?

• Automation - GitHub Actions

What is the best way to verify this PR?

Check if the CodeQL C++ workflow passes

PR submission checklist

• [x] This PR has tests
• [ ] This PR has documentation
• [ ] This PR has a CHANGELOG.md entry
• [x] This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)