Remove the Snyk badge from the README

We no longer use the Snyk service so it makes sense to remove the
badge.

Author: mcdonnnj

README.md

@@ -3,7 +3,6 @@
 [![GitHub Build Status](https://github.com/cisagov/skeleton-python-library/workflows/build/badge.svg)](https://github.com/cisagov/skeleton-python-library/actions)
 [![CodeQL](https://github.com/cisagov/skeleton-python-library/workflows/CodeQL/badge.svg)](https://github.com/cisagov/skeleton-python-library/actions/workflows/codeql-analysis.yml)
 [![Coverage Status](https://coveralls.io/repos/github/cisagov/skeleton-python-library/badge.svg?branch=develop)](https://coveralls.io/github/cisagov/skeleton-python-library?branch=develop)
-[![Known Vulnerabilities](https://snyk.io/test/github/cisagov/skeleton-python-library/develop/badge.svg)](https://snyk.io/test/github/cisagov/skeleton-python-library)
 
 This is a generic skeleton project that can be used to quickly get a
 new [cisagov](https://github.com/cisagov) Python library GitHub