Switch badge in README from Travis to GitHub Actions

Switch badge in README from Travis to GitHub Actions

diff --git a/README.md b/README.md
index e1a7002..e051608 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-[![Build Status](https://travis-ci.org/discourse/mini_scheduler.svg?branch=master)](https://travis-ci.org/discourse/mini_scheduler)
+[![Build Status](https://github.com/discourse/mini_scheduler/workflows/CI/badge.svg)](https://github.com/discourse/mini_scheduler/actions)
 [![Gem Version](https://badge.fury.io/rb/mini_scheduler.svg)](https://rubygems.org/gems/mini_scheduler)
 
 # mini_scheduler

GitHub sha: 3298834a

This commit appears in #7 which was approved by ZogStriP and davidtaylorhq. It was merged by gschlager.