Fix: remove unused (and broken) shields in README (#44)

Author: TrueBrain

README.md

@@ -1,11 +1,6 @@
 # openttd-helpers
 
 [![GitHub License](https://img.shields.io/github/license/OpenTTD/py-helpers)](https://github.com/OpenTTD/py-helpers/blob/main/LICENSE)
-[![GitHub Tag](https://img.shields.io/github/v/tag/OpenTTD/py-helpers?include_prereleases&label=stable)](https://github.com/OpenTTD/py-helpers/releases)
-[![GitHub commits since latest release](https://img.shields.io/github/commits-since/OpenTTD/py-helpers/latest/main)](https://github.com/OpenTTD/py-helpers/commits/main)
-
-[![GitHub Workflow Status (Testing)](https://img.shields.io/github/workflow/status/OpenTTD/py-helpers/Testing/main?label=main)](https://github.com/OpenTTD/py-helpers/actions?query=workflow%3ATesting)
-[![GitHub Workflow Status (Release)](https://img.shields.io/github/workflow/status/OpenTTD/py-helpers/Release?label=release)](https://github.com/OpenTTD/py-helpers/actions?query=workflow%3A%22Release%22)
 
 A repository full of small bits of Python code, commonly used in other
 projects developed for OpenTTD.