Fix URL

Remove superfluous `$`.

Author: martincostello

README.md

@@ -222,7 +222,7 @@ that are published to the [GitHub Container Registry][ghcr]. For example for the
 VERSION="main"
 IMAGE="ghcr.io/grafana/docker-otel-lgtm:${VERSION}"
 WORKFLOW="ghcr-image-build-and-publish.yml"
-IDENTITY="https://github.com/grafana/docker-otel-lgtm/.github/workflows/${WORKFLOW}$@refs/heads/${VERSION}"
+IDENTITY="https://github.com/grafana/docker-otel-lgtm/.github/workflows/${WORKFLOW}@refs/heads/${VERSION}"
 OIDC_ISSUER="https://token.actions.githubusercontent.com"
 
 cosign verify ${IMAGE} --certificate-identity ${IDENTITY} --certificate-oidc-issuer ${OIDC_ISSUER}