Remove travis from README (mentions master)

Author: manics

README.md

@@ -1,6 +1,5 @@
 # <a href="https://github.com/jupyterhub/repo2docker"><img src="https://raw.githubusercontent.com/jupyterhub/repo2docker/8731ecf0967cc5fde028c456f2b92be651ebbc18/docs/source/_static/images/repo2docker.png" height="48px" /> repo2docker</a>
 
-[![Deploy Status](https://travis-ci.org/jupyterhub/repo2docker.svg?branch=master)](https://travis-ci.org/jupyterhub/repo2docker)
 [![Build Status](https://github.com/jupyterhub/repo2docker/workflows/Continuous%20Integration/badge.svg)](https://github.com/jupyterhub/repo2docker/actions)
 [![Documentation Status](https://readthedocs.org/projects/repo2docker/badge/?version=latest)](http://repo2docker.readthedocs.io/en/latest/?badge=latest)
 [![Contribute](https://img.shields.io/badge/I_want_to_contribute!-grey?logo=jupyter)](https://repo2docker.readthedocs.io/en/latest/contributing/contributing.html)