Update Go version to 1.19.6

This is necessary to upgrade Go to version 1.19 in https://gitlab.com/gitlab-org/gitlab-runner

Part of 1/3

1. !8 (merged)
2. gitlab-org/ci-cd/runner-tools/runner-linters!7 (merged)
3. gitlab-org/gitlab-runner!3889 (merged)

It'd be nice if we had a lot of these version defined in one place only, and used across them all projects.