data wrangler tutorial link is broken on index.rst file

**Describe the bug**
The link to the AWS Data Wrangler tutorial is broken in the file index.rst. 

Current URL: https://github.com/awslabs/aws-data-wrangler/tree/latest/tutorials
Should be this URL: https://github.com/awslabs/aws-data-wrangler/tree/master/tutorials

**To Reproduce**
Click the link on https://aws-data-wrangler.readthedocs.io/   at the bottom of the page. 
