bump-formula-pr: always use HOMEBREW_PATH.
bump-formula-pr: always use HOMEBREW_PATH.

Fixes this when using environment filtering.

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