Update julia-nightly from 1.4 to 1.5 (#8437)
Update julia-nightly from 1.4 to 1.5 (#8437)

* Update julia-nightly from 1.4 to 1.5

* Specify julia-nightly as the target for the nightly cask

rogeriopradoj/homebrew-versions,caskroom/homebrew-versions,lantrix/homebrew-versions,pkq/homebrew-versions,pkq/homebrew-versions,lantrix/homebrew-versions,rogeriopradoj/homebrew-versions,mahori/homebrew-cask-versions,caskroom/homebrew-versions,404NetworkError/homebrew-versions,404NetworkError/homebrew-versions