Update badge for travis in README.md (#10717)

* Update README for updating travis badge

Update README cause
> This repository was migrated and is now building on travis-ci.com

* Update README.md

README.md

@@ -18,7 +18,7 @@
   -->
 
 [![Slack](https://img.shields.io/badge/slack-%23druid-72eff8?logo=slack)](https://s.apache.org/slack-invite)
-[![Build Status](https://travis-ci.org/apache/druid.svg?branch=master)](https://travis-ci.org/apache/druid)
+[![Build Status](https://api.travis-ci.com/apache/druid.svg?branch=master)](https://travis-ci.com/apache/druid)
 [![Language grade: Java](https://img.shields.io/lgtm/grade/java/g/apache/druid.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/apache/druid/context:java)
 [![Coverage Status](https://img.shields.io/codecov/c/gh/apache/druid)](https://codecov.io/gh/apache/druid)
 [![Docker](https://img.shields.io/badge/container-docker-blue.svg)](https://hub.docker.com/r/apache/druid)