Fix a broken link in CONTRIBUTING.md.
Fixes a broken link to "TensorFlow Style Guide":
@@ -89,7 +89,7 @@ Include a license at the top of new files.
### TensorFlow Guidelines.
* TensorFlow code should follow the
- [TensorFlow Style Guide](https://www.tensorflow.org/community/style_guide).
+ [TensorFlow Style Guide](https://www.tensorflow.org/community/contribute/code_style).
* TensorFlow code used with TFF should support both "graph mode" and "eager
mode" execution. Good eager-mode design principles should be followed,
