message: remove categories from sidenav
diff: - title: Philosophy
  url: /philosophy
  -
  -- title: Building Block Components
  - url: /components/building-blocks
  +- title: Components
  children:
  + - title: Avatar
  + url: /components/Avatar
  - title: BorderBox
  url: /components/BorderBox
  + - title: Box
  + url: /components/Box
  + - title: BranchName
  + url: /components/BranchName
  - title: Button
  url: /components/Button
  + - title: CircleBadge
  + url: /components/CircleBadge
  + - title: CircleOcticon
  + url: /components/CircleOcticon
  - title: CounterLabel
  url: /components/CounterLabel
  - title: Details
  url: /components/Dialog
  - title: Dropdown
  url: /components/Dropdown
  + - title: FilterList
  + url: /components/FilterList
  + - title: Flash
  + url: /components/Flash
  + - title: Flex
  + url: /components/Flex
  + - title: Grid
  + url: /components/Grid
  - title: Heading
  url: /components/Heading
  - title: Label
  url: /components/Link
  - title: PointerBox
  url: /components/PointerBox
  + - title: Position
  + url: /components/Position
  - title: StateLabel
  url: /components/StateLabel
  - title: StyledOcticon
  url: /components/StyledOcticon
  + - title: Text
  + url: /components/Text
  - title: TextInput
  url: /components/TextInput
  - title: Tooltip
  url: /components/Tooltip
  -
  -- title: Helper Components
  - url: /components/helper-components
  - children:
  - - title: Box
  - url: /components/Box
  - - title: Flex
  - url: /components/Flex
  - - title: Grid
  - url: /components/Grid
  - - title: Position
  - url: /components/Position
  - - title: Text
  - url: /components/Text
  -
  -
  -- title: Pattern Components
  - url: /components/pattern-components
  - children:
  - - title: Avatar
  - url: /components/Avatar
  - - title: BranchName
  - url: /components/BranchName
  - - title: CircleBadge
  - url: /components/CircleBadge
  - - title: CircleOcticon
  - url: /components/CircleOcticon
  - - title: FilterList
  - url: /components/FilterList
  - - title: Flash
  - url: /components/Flash
  - title: UnderlineNav
  url: /components/UnderlineNav
  