Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the issue has not already been raised

Issue

When opening a PR in Fastify repos a Snyk webhook is triggered, which checks if the PR has added any vulnerable dependencies:

GitHub have introduced their own GitHub Action that does the same thing.
With this we can remove the Snyk webhook from https://github.com/fastify/fastify/settings/hooks, and it'd be nice to get rid of another third-party dependency that may go down and cause issues, like how we removed Coveralls for similar reasons.