Remove deprecated Fission Nats connector (#2403)

We are removing Fission deprecated Nats connector and
planning to adopt Keda going forward to have better
delegated functionality and more rich support.

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>

skaffold.yaml

@@ -44,7 +44,6 @@ deploy:
         namespace: fission
         pprof.enabled: false
         canaryDeployment.enabled: false
-        nats.enabled: false
         influxdb.enabled: false
         pruneInterval: "60"
         repository: index.docker.io