Fix the travis widget to reflect the status of master.

PiperOrigin-RevId: 311482619

Author: julienvalentin

README.md

@@ -1,7 +1,7 @@
 # TensorFlow Graphics
 
 [![PyPI project status](https://img.shields.io/pypi/status/tensorflow-graphics.svg)](https://pypi.org/project/tensorflow-graphics/)
-[![Travis build status](https://img.shields.io/travis/tensorflow/graphics.svg)](https://travis-ci.org/tensorflow/graphics)
+[![Travis build status](https://img.shields.io/travis/tensorflow/graphics.svg?branch=master)](https://travis-ci.org/tensorflow/graphics)
 [![Supported Python version](https://img.shields.io/pypi/pyversions/tensorflow-graphics.svg)](https://pypi.org/project/tensorflow-graphics/)
 [![PyPI release version](https://img.shields.io/pypi/v/tensorflow-graphics.svg)](https://pypi.org/project/tensorflow-graphics/)