netdata: Adjust URL for live demo
It was discovered by our CI that there was a broken link for the remote link, but it was working. There is a redirect, but it seems that the CI does not count with that, and according to Netdata documentation [1], the demo was moved to london3. [2]
[1] https://learn.netdata.cloud/docs/agent/demo-sites [2] https://github.com/netdata/netdata/commit/a32cdea2aacad85a3a51bfbe2873822d46681235