workflows/tests: run brew style on Linux.
workflows/tests: run brew style on Linux.

linuxbrew-core seems to be passing `brew style` now (and has CI checks
to ensure it does in future, too).

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