Remove CodeCov badge

Author: mconcas

README.md

@@ -2,7 +2,6 @@
 
 <!--  /// \cond EXCLUDE_FOR_DOXYGEN -->
 
-[![codecov](https://codecov.io/gh/AliceO2Group/AliceO2/branch/dev/graph/badge.svg)](https://codecov.io/gh/AliceO2Group/AliceO2/branches/dev)
 [![JIRA](https://img.shields.io/badge/JIRA-Report%20issue-blue.svg)](https://alice.its.cern.ch/jira/secure/CreateIssue.jspa?pid=11201&issuetype=1)
 [![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.1493334.svg)](https://doi.org/10.5281/zenodo.1493334)