Update absolute same-site links within Finance.
This makes absolute same-site links within https://about.gitlab.com/handbook/finance/ relative to the site root. It also removes an explicit "index.html" for URL tidiness and resilience.
This makes absolute same-site links within https://about.gitlab.com/handbook/finance/ relative to the site root. It also removes an explicit "index.html" for URL tidiness and resilience.