Fix coveralls badge

Author: minikin

README.md

@@ -14,9 +14,8 @@
   <a href="https://github.com/input-output-hk/catalyst-core/blob/main/CODE_OF_CONDUCT.md">
     <img src="https://img.shields.io/badge/PRs-welcome-brightgreen.svg" alt="PRs welcome!" />
   </a>
-  <a href='https://coveralls.io/github/input-output-hk/catalyst-core?branch=main'>
-    <img src='https://coveralls.io/repos/github/input-output-hk/catalyst-core/badge.svg?branch=main' alt='Coverage Status' />
-  </a>
+   <a href='https://coveralls.io/github/input-output-hk/catalyst-core?branch=feature/add-ci-coveralls'><img src='https://coveralls.io/repos/github/input-output-hk/catalyst-core/badge.svg?branch=feature/add-ci-coveralls' alt='Coverage Status' />
+</a>
 </p>
 
 # Content