remove the docs for stuff i didn't do

docs/configuration/frontend_management.md

@@ -19,14 +19,7 @@ config :pleroma, :frontends,
   admin: %{
     "name" => "admin",
     "ref" => "develop"
-  },
-  dwarves: %{
-    "name" => "diggydiggy",
-    "ref" => "hole"
-  },
-  extra: [
-    %{"subdomain" => "dwarves", "key" => :dwarves}
-  ]
+  }
 ```
 
 This would serve the frontend from the the folder at `$instance_static/frontends/pleroma/stable`. You have to copy the frontend into this folder yourself. You can choose the name and ref any way you like, but they will be used by mix tasks to automate installation in the future, the name referring to the project and the ref referring to a commit.