Documentation - Fix mMissing Menu Prefix in example (#10599)

CONTRIBUTORS.rst

@@ -719,6 +719,7 @@ Contributors
 * Thiago C. S. Tioma
 * Kevin Chung (kev-odin)
 * valnuro
+* Vitaly Babiy
 
 Translators
 ===========

docs/topics/snippets/customising.md

@@ -159,7 +159,7 @@ class ProductViewSet(SnippetViewSet):
 
 class MarketingViewSetGroup(SnippetViewSetGroup):
     items = (AdvertViewSet, ProductViewSet)
-    icon = "folder-inverse"
+    menu_icon = "folder-inverse"
     menu_label = "Marketing"
     menu_name = "marketing"