doc: Improve wording on “Go on Docker Hub” use case

Signed-off-by: Helder Correia <174525+helderco@users.noreply.github.com>

docs/tests/use-cases/ci-cd-for-go-project/push.cue.fragment

@@ -7,8 +7,8 @@ push: {
 		"image": image.output
 		dest:    "\(_dockerUsername)/<my_repository>"
 		auth: {
-			username: "\(_dockerUsername)"
+			username: _dockerUsername
 			secret:   client.env.DOCKER_PASSWORD
 		}
 	}
-}
+}