Remove the travis badge

Author: jimhester

README.md

@@ -2,7 +2,6 @@
 
 <!-- badges: start -->
 [![R build status](https://github.com/r-lib/xml2/workflows/R-CMD-check/badge.svg)](https://github.com/r-lib/xml2/actions)
-[![Travis Build Status](https://travis-ci.org/r-lib/xml2.svg?branch=master)](https://travis-ci.org/r-lib/xml2)
 [![Coverage Status](https://img.shields.io/codecov/c/github/r-lib/xml2/master.svg)](https://codecov.io/github/r-lib/xml2?branch=master)
 <!-- badges: end -->