README: fix dead link in spack badge

cf. spack/spack#46604

README.md

@@ -3,7 +3,7 @@
 [![Build Status](https://jenkins-sim.informatik.uni-stuttgart.de/buildStatus/icon?job=DisCoTec%2Fmain)](https://jenkins-sim.informatik.uni-stuttgart.de/job/DisCoTec/job/main/)
 [![License: LGPL v3](https://img.shields.io/badge/License-LGPL_v3-blue.svg)](https://www.gnu.org/licenses/lgpl-3.0)
 [![Zenodo DOI](https://zenodo.org/badge/226341053.svg)](https://zenodo.org/badge/latestdoi/226341053)
-[![Latest spack version](https://img.shields.io/spack/v/discotec)](https://spack.readthedocs.io/en/latest/package_list.html#discotec)
+[![Latest spack version](https://img.shields.io/spack/v/discotec)](https://packages.spack.io/package.html?name=discotec)
 [![Codacy Badge](https://app.codacy.com/project/badge/Grade/cac5bc0841784657b2bb75ea46e7cf01)](https://app.codacy.com/gh/SGpp/DisCoTec/dashboard)
 
 ## What is DisCoTec?