Tidy "ruledocsgen" module for github.com/JohannesKaufmann/html-to-markdown bump

Go 1.17 has a different handling of dependencies. By default, it emulates the old behavior for compatibility with older
Go versions. The Dependabot PRs are produced in this manner.

This project now uses Go 1.17 exclusively, as is indicated by the `go` directive and by the contributor guide. There is
no need to provide compatibility with unsupported Go versions, so we use the `-compat=1.17` flag in the `go mod tidy`
command, as is done here.

Author: per1234