Improve codefence (#9973)

#9830 (comment)

Co-authored-by: Jon Galloway <[email protected]>

Author: martincostello

release-notes/10.0/preview/preview6/sdk.md

@@ -93,7 +93,7 @@ dotnet clean --cli-schema
 
 Outputs:
 
-```json
+```jsonc
 {
   "name": "clean",
   "version": "10.0.100-dev",