Revert "composedPlugin should have its own prefix context (#368)"

This reverts commit c1685f4.

index.js

@@ -81,22 +81,16 @@ const fastifyAutoload = async function autoload (fastify, options) {
           // encapsulate hooks at plugin level
           app.register(hookPlugin)
         }
-        registerAllPlugins(app, pluginFiles, true)
+        registerAllPlugins(app, pluginFiles)
       }
-
-      fastify.register(composedPlugin, { prefix: options.options?.prefix ?? prefix })
+      fastify.register(composedPlugin)
     }
   }
 
-  function registerAllPlugins (app, pluginFiles, composed = false) {
+  function registerAllPlugins (app, pluginFiles) {
     for (const pluginFile of pluginFiles) {
       // find plugins for this prefix, based on filename stored in registerPlugins()
       const plugin = metas.find((i) => i.filename === pluginFile.file)
-
-      if (composed) {
-        plugin.options.prefix = undefined
-      }
-
       // register plugins at fastify level
       if (plugin) registerPlugin(app, plugin, pluginsMeta)
     }