juju 2.8.1
juju 2.8.1

Move juju to 2.8.1

This moves juju to 2.8.1 and removes the version_scheme 1, as we're
moving forward in versions.

Juju has updated it's release process, so any new releases that aren't
intended to be picked up by the livecheck are now tagged as
pre-releases.

 - Version scheme needs to stay it seems

Closes #57904.

Signed-off-by: Dawid Dziurla <c4a7db180859322ef5630a1dfc2805b5bc97fc25@gmail.com>
Signed-off-by: BrewTestBot <8a898ee6867e4f2028e63d2a6319b2224641c06c@users.noreply.github.com>

dsXLII/homebrew-core,maxim-belkin/homebrew-core,spaam/homebrew-core,mbcoguno/homebrew-core,stgraber/homebrew-core,Homebrew/homebrew-core,filcab/homebrew-core,cblecker/homebrew-core,maxim-belkin/homebrew-core,chrisfinazzo/homebrew-core,nbari/homebrew-core,Moisan/homebrew-core,sjackman/homebrew-core,dsXLII/homebrew-core,rwhogg/homebrew-core,uyjulian/homebrew-core,adam-moss/homebrew-core,jabenninghoff/homebrew-core,mbcoguno/homebrew-core,chrisfinazzo/homebrew-core,JCount/homebrew-core,jvillard/homebrew-core,mahori/homebrew-core,lemzwerg/homebrew-core,spaam/homebrew-core,adam-moss/homebrew-core,jvillard/homebrew-core,rwhogg/homebrew-core,makigumo/homebrew-core,jabenninghoff/homebrew-core,Homebrew/homebrew-core,stgraber/homebrew-core,Linuxbrew/homebrew-core,nandub/homebrew-core,Moisan/homebrew-core,lembacon/homebrew-core,mbcoguno/homebrew-core,uyjulian/homebrew-core,lemzwerg/homebrew-core,zyedidia/homebrew-core,nandub/homebrew-core,mfikes/homebrew-core,makigumo/homebrew-core,cblecker/homebrew-core,JCount/homebrew-core,nbari/homebrew-core,mfikes/homebrew-core,mahori/homebrew-core,jvillard/homebrew-core,Linuxbrew/homebrew-core,lembacon/homebrew-core,zyedidia/homebrew-core,sjackman/homebrew-core,lembacon/homebrew-core,filcab/homebrew-core