upgrade.rb: Fix plural_s when number = 0
upgrade.rb: Fix plural_s when number = 0

Currently Upgrade prints out:
"Upgrading 0 outdated package, with result:"

This change makes it print:
"Upgrading 0 outdated packages, with result:"
correctly pluralizing "packages".

Closes Homebrew/homebrew#22854.

Signed-off-by: Adam Vandenberg <34c2b6407fd5a10249a15d699d40f9ed1782e98c@gmail.com>

gordonmcshane/homebrew,nandub/brew,MikeMcQuaid/brew,zmwangx/brew,palxex/brew,EricFromCanada/brew,claui/brew,vitorgalvao/brew,reelsense/brew,mistydemeo/homebrew,rwhogg/brew,mistydemeo/homebrew,mgrimes/brew,JCount/brew,mahori/brew,sjackman/homebrew,JCount/brew,mahori/brew,Linuxbrew/brew,pseudocody/brew,jmsundar/brew,aw1621107/brew,toonetown/homebrew,mgrimes/brew,muellermartin/dist,EricFromCanada/brew,amar-laksh/brew_sudo,staticfloat/brew,maxim-belkin/brew,MikeMcQuaid/brew,vitorgalvao/brew,toonetown/homebrew,AnastasiaSulyagina/brew,hanxue/linuxbrew,konqui/brew,konqui/brew,bfontaine/brew,alyssais/brew,tonyg/homebrew,Homebrew/brew,alyssais/brew,maxim-belkin/brew,MikeMcQuaid/brew,Homebrew/brew,AnastasiaSulyagina/brew,reitermarkus/brew,vitorgalvao/brew,Linuxbrew/brew,sjackman/homebrew,palxex/brew,palxex/brew,nandub/brew,staticfloat/brew,JCount/brew,bfontaine/brew,Linuxbrew/brew,DomT4/brew,mgrimes/brew,gregory-nisbet/brew,DomT4/brew,zmwangx/brew,maxim-belkin/brew,ilovezfs/brew,sjackman/homebrew,DomT4/brew,rwhogg/brew,jmsundar/brew,rwhogg/brew,EricFromCanada/brew,pseudocody/brew,tonyg/homebrew,staticfloat/brew,jmsundar/brew,claui/brew,gregory-nisbet/brew,amar-laksh/brew_sudo,MikeMcQuaid/brew,muellermartin/dist,vitorgalvao/brew,alyssais/brew,gordonmcshane/homebrew,reitermarkus/brew,mistydemeo/homebrew,mahori/brew,ilovezfs/brew,DomT4/brew,gordonmcshane/homebrew,reitermarkus/brew,EricFromCanada/brew,claui/brew,reelsense/brew,tonyg/homebrew,aw1621107/brew,Linuxbrew/brew,pseudocody/brew,JCount/brew,AnastasiaSulyagina/brew,amar-laksh/brew_sudo,aw1621107/brew,toonetown/homebrew,muellermartin/dist,ilovezfs/brew,nandub/brew,mahori/brew,konqui/brew,bfontaine/brew,konqui/brew,hanxue/linuxbrew,gregory-nisbet/brew,zmwangx/brew,sjackman/homebrew,nandub/brew,Homebrew/brew,reelsense/brew,reitermarkus/brew,hanxue/linuxbrew,claui/brew,Homebrew/brew