Increase hiedb version since format change

[soulomoon]

@jhrcek Just randomly found https://github.com/haskell/haskell-language-server/blob/master/ghcide/session-loader/Development/IDE/Session.hs#L226, do we need to increase this to invalidate existing hiedb databases?

Originally posted by @fendor in #4635 (comment)