docs: update badge link

Noticed the badge was showing a failing status even though the CI appeared to be passing.

README.md

@@ -1,6 +1,6 @@
 # OpenTelemetry-Go
 
-[![CI](https://github.com/open-telemetry/opentelemetry-go/workflows/ci/badge.svg)](https://github.com/open-telemetry/opentelemetry-go/actions?query=workflow%3Aci+branch%3Amain)
+[![ci](https://github.com/open-telemetry/opentelemetry-go/actions/workflows/ci.yml/badge.svg?branch=main)](https://github.com/open-telemetry/opentelemetry-go/actions/workflows/ci.yml)
 [![codecov.io](https://codecov.io/gh/open-telemetry/opentelemetry-go/coverage.svg?branch=main)](https://app.codecov.io/gh/open-telemetry/opentelemetry-go?branch=main)
 [![PkgGoDev](https://pkg.go.dev/badge/go.opentelemetry.io/otel)](https://pkg.go.dev/go.opentelemetry.io/otel)
 [![Go Report Card](https://goreportcard.com/badge/go.opentelemetry.io/otel)](https://goreportcard.com/report/go.opentelemetry.io/otel)