spec_helper: fix etc leak.
spec_helper: fix etc leak.

Fix the `etc/bash_completion.d/_brew_services` leak from the new
bash completion in the Homebrew/homebrew-services tap.

konqui/brew,maxim-belkin/brew,nandub/brew,alyssais/brew,mahori/brew,reelsense/brew,vitorgalvao/brew,ilovezfs/brew,jmsundar/brew,nandub/brew,aw1621107/brew,vitorgalvao/brew,sjackman/homebrew,DomT4/brew,hanxue/linuxbrew,reitermarkus/brew,pseudocody/brew,jmsundar/brew,claui/brew,JCount/brew,Linuxbrew/brew,reitermarkus/brew,reelsense/brew,Homebrew/brew,nandub/brew,alyssais/brew,MikeMcQuaid/brew,Homebrew/brew,palxex/brew,EricFromCanada/brew,aw1621107/brew,maxim-belkin/brew,Homebrew/brew,reitermarkus/brew,reitermarkus/brew,hanxue/linuxbrew,vitorgalvao/brew,sjackman/homebrew,aw1621107/brew,MikeMcQuaid/brew,alyssais/brew,claui/brew,mahori/brew,mgrimes/brew,mgrimes/brew,maxim-belkin/brew,DomT4/brew,vitorgalvao/brew,Linuxbrew/brew,EricFromCanada/brew,mahori/brew,sjackman/homebrew,mgrimes/brew,EricFromCanada/brew,palxex/brew,hanxue/linuxbrew,ilovezfs/brew,konqui/brew,konqui/brew,claui/brew,konqui/brew,JCount/brew,sjackman/homebrew,claui/brew,reelsense/brew,JCount/brew,JCount/brew,jmsundar/brew,nandub/brew,Homebrew/brew,EricFromCanada/brew,palxex/brew,pseudocody/brew,MikeMcQuaid/brew,Linuxbrew/brew,ilovezfs/brew,pseudocody/brew,DomT4/brew,DomT4/brew,mahori/brew,MikeMcQuaid/brew,Linuxbrew/brew