remove mention of product-config from env-var docs

Author: adwk67

docs/modules/airflow/pages/reference/environment-variables.adoc

@@ -33,32 +33,6 @@ docker run \
 oci.stackable.tech/sdp/airflow-operator:0.0.0-dev
 ----
 
-== PRODUCT_CONFIG
-
-*Default value*: `/etc/stackable/airflow-operator/config-spec/properties.yaml`
-
-*Required*: false
-
-*Multiple values*: false
-
-[source]
-----
-export PRODUCT_CONFIG=/foo/bar/properties.yaml
-stackable-airflow-operator run
-----
-
-or via docker:
-
-----
-docker run \
-    --name airflow-operator \
-    --network host \
-    --env KUBECONFIG=/home/stackable/.kube/config \
-    --env PRODUCT_CONFIG=/my/product/config.yaml \
-    --mount type=bind,source="$HOME/.kube/config",target="/home/stackable/.kube/config" \
-    oci.stackable.tech/sdp/airflow-operator:0.0.0-dev
-----
-
 == WATCH_NAMESPACE
 
 *Default value*: All namespaces