refactor: remove usage of deprecated request.routeConfig (#530)

Author: inyourtime

index.js

@@ -387,9 +387,7 @@ async function fastifyStatic (fastify, opts) {
  }
 
  async function serveFileHandler (req, reply) {
- // TODO: remove the fallback branch when bump major
- /* c8 ignore next */
- const routeConfig = req.routeOptions?.config || req.routeConfig
+ const routeConfig = req.routeOptions?.config
  return pumpSendToReply(req, reply, routeConfig.file, routeConfig.rootPath)
  }
 }