docs: "Sourcing from Contentful" is not stub anymore (#9492)
docs: "Sourcing from Contentful" is not stub anymore (#9492)

Removing Prose because it's not a major CMS. Contentful article is not a stub anymore.
ChristopherBiscardi/gatsby,0x80/gatsby,mingaldrichgan/gatsby,mingaldrichgan/gatsby,ChristopherBiscardi/gatsby,0x80/gatsby,ChristopherBiscardi/gatsby,mingaldrichgan/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,0x80/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,ChristopherBiscardi/gatsby