cleanup: don't remove portable ruby on periodic cleanups.
cleanup: don't remove portable ruby on periodic cleanups.

Otherwise we end up deleting the running Ruby version.

Fixes #5707.

nandub/brew,MikeMcQuaid/brew,reitermarkus/brew,Homebrew/brew,EricFromCanada/brew,nandub/brew,nandub/brew,konqui/brew,EricFromCanada/brew,mahori/brew,claui/brew,Homebrew/brew,sjackman/homebrew,mahori/brew,MikeMcQuaid/brew,vitorgalvao/brew,JCount/brew,EricFromCanada/brew,konqui/brew,claui/brew,EricFromCanada/brew,vitorgalvao/brew,vitorgalvao/brew,MikeMcQuaid/brew,reitermarkus/brew,sjackman/homebrew,vitorgalvao/brew,reitermarkus/brew,nandub/brew,konqui/brew,Homebrew/brew,claui/brew,mahori/brew,Homebrew/brew,reitermarkus/brew,sjackman/homebrew,JCount/brew,JCount/brew,claui/brew,MikeMcQuaid/brew,konqui/brew,sjackman/homebrew,JCount/brew,mahori/brew