Always use Sandy wrapper

Summary:
Since the Sandy wrapper is now rolled out to 100%, removing the GK. Further code cleanup in next diffs.

Changelog: Flipper that don't use the new Sandy plugin format yet (see https://fbflipper.com/docs/extending/sandy-migration) will now always be loaded inside a legacy container

Reviewed By: timur-valiev

Differential Revision: D29394736

fbshipit-source-id: f7a7c321c6b6a82470d47e4352d86135c3849b82

desktop/app/src/dispatcher/plugins.tsx

@@ -318,22 +318,8 @@ const requirePluginInternal = (
     plugin.packageName = pluginDetails.name;
     plugin.details = pluginDetails;
 
-    if (
-      GK.get('flipper_use_sandy_plugin_wrapper') ||
-      process.env.NODE_ENV === 'test'
-    ) {
     return createSandyPluginFromClassicPlugin(pluginDetails, plugin);
   }
-
-    // set values from package.json as static variables on class
-    Object.keys(pluginDetails).forEach((key) => {
-      if (key !== 'name' && key !== 'id') {
-        plugin[key] =
-          plugin[key] || pluginDetails[key as keyof ActivatablePluginDetails];
-      }
-    });
-  }
-  return plugin;
 };
 
 export function createSandyPluginFromClassicPlugin(