fix: ensure path imports correctly

Author: jakebolam

src/handler.js

@@ -1,5 +1,5 @@
 // TODO: put back on release of: https://github.com/probot/serverless-lambda/pull/13/files
 // const { serverless } = require('@probot/serverless-lambda')
-const { serverless } = require('serverless-lambda')
+const { serverless } = require('./serverless-lambda')
 const appFn = require('./')
 module.exports.probot = serverless(appFn)