fix: move Deck demos docs

Author: nicolethoen

packages/module/patternfly-docs/content/extensions/component-groups/examples/Deck/DeckDemos.md

@@ -1,8 +1,8 @@
 ---
 # Sidenav top-level section
 # should be the same for all markdown files
-section: Component groups
-subsection: Content containers
+section: extensions
+subsection: component-groups
 # Sidenav secondary level section
 # should be the same for all markdown files
 id: Deck
@@ -23,4 +23,4 @@ A complete onboarding experience using ModalDeck to guide users through key prod
 
 ```ts file="./OnboardingModalDeckDemo.tsx"
 
-```
+```