Remove test coverage badge

Removed test coverage badge from README.

Author: kkbrum

README.md

@@ -6,7 +6,6 @@
 <!-- badges: start -->
 
 [![R-CMD-check](https://github.com/kkbrum/optrefine/actions/workflows/R-CMD-check.yaml/badge.svg)](https://github.com/kkbrum/optrefine/actions/workflows/R-CMD-check.yaml)
-[![test-coverage](https://github.com/kkbrum/optrefine/actions/workflows/test-coverage.yaml/badge.svg)](https://github.com/kkbrum/optrefine/actions/workflows/test-coverage.yaml)
 <!-- badges: end -->
 
 The goal of optrefine is to split existing strata (or none) into more