Using ghc_version: head breaks; this URL is a 404:

It would be great for one of the following to occur:

1. Fix the URL (e.g. https://gitlab.haskell.org/ghc/ghc/-/jobs/artifacts/master/raw/ghc-x86_64-linux-fedora33-release.tar.xz?job=x86_64-linux-fedora33-release)
2. Enable GHCup's nightly feature: https://discourse.haskell.org/t/ann-ghcup-0-1-19-3-released/6749

It seems like all that's needed for (2) is to upgrade GHCup installed by this action to 0.1.19.3 + set

ghc-version: latest-nightly
ghcup-release-channel: https://ghc.gitlab.haskell.org/ghcup-metadata/ghcup-nightlies-0.0.7.yaml