Remove Luxor pool from site

[rrs94]

Issue Summary

It seems LBC cannot be mined anymore on Luxor, page throws a 404: https://mining.luxor.tech/coins/lbry

It is not listed as a mineable coin in the home page either. I can remove the link and make a PR however I'm not sure what to replace it with on this page: https://lbry.com/faq/mining-credits

That page contains instructions on setup for Luxor, I can replace the instructions to be for another pool, just don't know which.

Steps to Reproduce

1. Go to https://lbry.com/faq/mining-pools
2. Click on Luxor link
3. Page shows a 404