Fix the build badge after github change (#155)

See the instructions here badges/shields#8671

README.md

@@ -12,7 +12,7 @@
   <a href="https://pkg.go.dev/github.com/open-telemetry/opamp-go">
     <img alt="Go Docs" height="28" src="https://godoc.org/github.com/open-telemetry/opamp-go?status.svg"></a>
   <a href="https://github.com/open-telemetry/opamp-go/actions/workflows/build-and-test.yml?query=branch%3Amain">
-    <img alt="Build Status" src="https://img.shields.io/github/workflow/status/open-telemetry/opamp-go/build-and-test/main?style=for-the-badge"></a>
+    <img alt="Build Status" src="https://img.shields.io/github/actions/workflow/status/open-telemetry/opamp-go/build-and-test.yml?branch%3Amain&style=for-the-badge"></a>
   <a href="https://goreportcard.com/report/github.com/open-telemetry/opamp-go">
     <img alt="Go Report Card" src="https://goreportcard.com/badge/github.com/open-telemetry/opamp-go?style=for-the-badge"></a>
   <a href="https://codecov.io/gh/open-telemetry/opamp-go/branch/main/">