Drop Smart Proxy plugin testing

[ekohl]

All plugins have been converted to GitHub Actions and this cleans up the remains.

[ekohl]

This is failing and now I'm leaning to just cleaning it all up:

• Use GitHub Actions for CI smart_proxy_dhcp_infoblox#58
• Use GitHub Actions for CI smart_proxy_dhcp_remote_isc#8
• Use GitHub Actions for CI smart_proxy_discovery#18
• Use the smart_proxy_plugin.yml reusable GHA workflow smart_proxy_dns_infoblox#34
• Use GitHub Actions for CI smart_proxy_monitoring#35
• Use GitHub Actions for CI smart_proxy_omaha#27
• Use the smart_proxy_plugin.yml reusable GHA workflow smart_proxy_salt#95

Pulp already has been converted.

[ekohl]

When merging this, we should also clean up bot access on the specific repositories.

[ekohl]

And now also cleaned up access for the bot in the various repos.