Delete reference to license key in envoy-tutorial-standalone-envoy.md (#7466)

Apparently setting a license key is not (longer?) needed. The tutorial doesn't mention it in the rest of the text as the deleted line promises. I couldn't find a hidden statement about a license key in the config files. Not does the page on installing opa using docker mention a license key. https://www.openpolicyagent.org/docs/latest/deployments/

Signed-off-by: Joost Holslag <[email protected]>

Author: joostholslag

docs/content/envoy-tutorial-standalone-envoy.md

@@ -336,7 +336,6 @@ There are a few things to note:
   created earlier.
 * The OPA container is configured to download policy bundles from
   the in-cluster bundle server (`bundle-server.default.svc.cluster.local`).
-* The OPA license key must be set. We show how to do this in the next step.
 
 ```yaml
 # app.yaml