Update base dependency given that GHC 9.6 is now the oldest stable release

[changlinli]

base-4.18 (GHC 9.6) is now the oldest stable release while right now that is excluded since the base dependency of this package is < 4.18. GHC 9.10 is up to base-4.20. I see that @cdornan has previously updated the Hackage metadata to widen the dependency bounds. Can we do that again, at least to include base-4.18, but ideally up to base-4.20? Otherwise we can't use argon2 on current supported GHC versions.