Docs/Setup.md contains an outdated or broken Helm Chart link

Hello! I was speaking with a member of the matrix-hookshot channel and was informed to create an issue as the docs/setup.md file contains a broken link to the helm chart and guide for helm for hookshot.

The current links for the helm chart go to https://matrix-org.github.io/helm/hookshot/ "...defined in helm/hookshot that can..."

and https://github.com/matrix-org/matrix-hookshot/helm/hookshot/README.md "...method is available here."

Open docs/setup.md and inspect the two Helm chart links identified in the issue. Verify the appropriate current chart and guide URLs, then update the links so both resolve to the maintained Helm documentation and chart location.

Written by the indexing model from the issue text.