Update query timing link

The query timing link is broken (example comment: gitlab-org/gitlab!140989 (comment 1714050365))

This MR updates the link and all of the fixtures

old link: https://docs.gitlab.com/ee/development/query_performance.html#timing-guidelines-for-queries

new link: https://docs.gitlab.com/ee/development/database/query_performance.html#timing-guidelines-for-queries