Examples under Checks section of Using k6 seem outdated

[Shobhit-Nagpal]

Hi!

I was going through the Checks section of the documentation and found that the scripts mentioned here seem outdated

Few examples have switched to using https://quickpizza.grafana.com while this page uses http://test.k6.io. Even the checks mentioned in the section fail as test.k6.io redirects to quickpizza.grafana.com, which according to the response i checked, seems to be a svelte site. hence the content to check in it would be the title text instead of any heading text, etc

If this issue is correct, I'll open the PR to fix this