Update Navigation-and-menus.markdown
Update Navigation-and-menus.markdown

I'm going through the docs as I try to understand Orchard better. The English in the second sentence has always struck me a little weird, so I made the change to mean the same thing but to sound better grammatically.
armanforghani/OrchardDoc,phillipsj/OrchardDoc,wharri220/OrchardDoc,rtpHarry/OrchardDoc,dcinzona/OrchardDoc,MetSystem/OrchardDoc,abhishekluv/OrchardDoc,dcinzona/OrchardDoc,wharri220/OrchardDoc,rtpHarry/OrchardDoc,wharri220/OrchardDoc,SzymonSel/OrchardDoc,MetSystem/OrchardDoc,dcinzona/OrchardDoc,phillipsj/OrchardDoc,OrchardCMS/OrchardDoc,OrchardCMS/OrchardDoc,phillipsj/OrchardDoc,SzymonSel/OrchardDoc,armanforghani/OrchardDoc,rtpHarry/OrchardDoc,abhishekluv/OrchardDoc,SzymonSel/OrchardDoc,armanforghani/OrchardDoc,abhishekluv/OrchardDoc,MetSystem/OrchardDoc