chore: fix workflow status badge URL

Author: lopburny

README.md

@@ -1,5 +1,5 @@
 ![serverless](http://public.serverless.com/badges/v3.svg)
-![workflow status](https://github.com/serverless-operations/serverless-apigateway-service-proxy/actions/workflows/config/badge.svg)
+![workflow status](https://github.com/serverless-operations/serverless-apigateway-service-proxy/actions/workflows/config.yml/badge.svg)
 [![npm version](https://badge.fury.io/js/serverless-apigateway-service-proxy.svg)](https://badge.fury.io/js/serverless-apigateway-service-proxy)
 [![Coverage Status](https://coveralls.io/repos/github/horike37/serverless-apigateway-service-proxy/badge.svg?branch=master)](https://coveralls.io/github/horike37/serverless-apigateway-service-proxy?branch=master)
 [![MIT License](http://img.shields.io/badge/license-MIT-blue.svg?style=flat)](LICENSE)