Update GitHub Actions badge to pull main branch status only.

README.md

@@ -3,7 +3,7 @@
   <p align="center">An <b>experimental</b> CQL execution engine for analyzing FHIR healthcare data at
 scale</p>
   <p align="center">
-    <a href="https://github.com/google/cql/actions"><img src="https://github.com/google/cql/workflows/go_test/badge.svg" alt="GitHub Actions Build Status"/></a>
+    <a href="https://github.com/google/cql/actions/workflows/go_build.yaml?query=branch%3Amain"><img src="https://github.com/google/cql/actions/workflows/go_build.yaml/badge.svg?branch=main" alt="GitHub Actions Build Status"/></a>
     <a href="https://godoc.org/github.com/google/cql"><img src="https://godoc.org/github.com/google/cql?status.svg" alt="Go Documentation"/></a>
   </p>
 </p>