chore: remove hardcoded coverage badge, fix Python version badge (#43)

Author: croc100

README.md

@@ -6,9 +6,8 @@
   <a href="https://github.com/croc100/pytest-mrt/network/dependents"><img src="https://img.shields.io/badge/used%20by-see%20dependents-informational" alt="Used by"></a>
   <a href="https://github.com/croc100/pytest-mrt/actions"><img src="https://img.shields.io/github/actions/workflow/status/croc100/pytest-mrt/ci.yml?branch=main&label=tests" alt="CI"></a>
   <a href="https://codecov.io/gh/croc100/pytest-mrt"><img src="https://codecov.io/gh/croc100/pytest-mrt/graph/badge.svg?token=CODECOV_TOKEN" alt="Coverage"></a>
-  <img src="https://img.shields.io/badge/coverage-81%25-yellowgreen" alt="Coverage 81%">
   <img src="https://img.shields.io/badge/status-stable-brightgreen" alt="Production/Stable">
-  <a href="https://pypi.org/project/pytest-mrt"><img src="https://img.shields.io/pypi/pyversions/pytest-mrt" alt="Python"></a>
+  <img src="https://img.shields.io/badge/python-3.10%20%7C%203.11%20%7C%203.12%20%7C%203.13-blue" alt="Python 3.10-3.13">
   <img src="https://img.shields.io/badge/license-MIT-green" alt="MIT License">
 </p>