Remove broken Travis build shield

[ci skip]

Author: probonopd

README.md

@@ -1,4 +1,4 @@
-# AppImageKit [![Build Status](https://travis-ci.org/AppImage/AppImageKit.svg?branch=appimagetool/master)](https://travis-ci.org/AppImage/AppImageKit) ![Downloads](https://img.shields.io/github/downloads/AppImage/AppImageKit/total.svg) [![irc](https://img.shields.io/badge/IRC-%23AppImage%20on%20libera.chat-blue.svg)](https://web.libera.chat/#AppImage) [![Donate](https://img.shields.io/badge/Donate-PayPal-green.svg)](https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=ZT9CL8M5TJU72)
+# AppImageKit ![Downloads](https://img.shields.io/github/downloads/AppImage/AppImageKit/total.svg) [![irc](https://img.shields.io/badge/IRC-%23AppImage%20on%20libera.chat-blue.svg)](https://web.libera.chat/#AppImage) [![Donate](https://img.shields.io/badge/Donate-PayPal-green.svg)](https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=ZT9CL8M5TJU72)
 
 The __AppImage__ format is a format for packaging applications in a way that allows them to
 run on a variety of different target systems (base operating systems, distributions) without further modification.