DEV: Remove decoration for legacy hamburger menu (#160)

The `legacy` option has been removed from the `navigation_menu` site setting, so we can remove all the logic that's related to the `legacy` option from this plugin.

Internal topic: t/113137.

assets/javascripts/discourse/initializers/setup-docs.js

@@ -46,22 +46,12 @@ export default {
     }
 
     withPluginApi("1.2.0", (api) => {
-      if (siteSettings.navigation_menu !== "legacy") {
       api.addCommunitySectionLink({
         name: "docs",
         route: "docs.index",
         title: I18n.t("sidebar.docs_link_title"),
         text: I18n.t("sidebar.docs_link_text"),
       });
-      } else {
-        api.decorateWidget("hamburger-menu:generalLinks", () => {
-          return {
-            route: "docs",
-            label: "docs.title",
-            className: "docs-link",
-          };
-        });
-      }
     });
   },
 };