Docs: Remove Python 3.7 advertisement

This patch removes Python 3.7 from our supported versions list in the
README.  It also fixes a syntax error in the same list, causing
version 3.12 to be rendered as 3.1220.

Signed-off-by: Patrick M. Niedzielski <pniedzielski@bloomberg.net>

Author: pniedzielski

README.md

@@ -19,7 +19,7 @@
 [![MessageQueue](https://img.shields.io/badge/MessageQueue-blue)](#)
 [![Documentation](https://img.shields.io/badge/Documentation-blue)](https://bloomberg.github.io/blazingmq)
 [![Code Style](https://img.shields.io/badge/Black-black)](#)
-![Supported Python versions](https://img.shields.io/badge/python-3.7%20%7C%203.8%20%7C%203.9%20%7C%203.10%20%7C%203.11%20%7C%203.1220%7C%203.13-blue?logo=python)
+![Supported Python versions](https://img.shields.io/badge/python-3.8%20%7C%203.9%20%7C%203.10%20%7C%203.11%20%7C%203.12%20%7C%203.13-blue?logo=python)
 
 # BlazingMQ Python SDK