Revert "Add Feature Preview documentation (#846)" (#850)

This reverts commit 3001a7a.

Author: gtsiolis

src/docs/feature-preview.md

@@ -107,10 +107,6 @@ export const MENU: MenuEntry[] = [
             ),
         ]
     ),
-    M(
-        "Feature Preview",
-        "feature-preview",
-    ),
     M(
         "Gitpod Self-Hosted",
         "self-hosted/latest/self-hosted",