chore(rh-shield-operator): add 'maintainer' label

Release 1.11.0 of the `preflight` utility used to certify
the Operator images updated the `HasRequiredLabels` test and
the test now fails if the `maintainer` label has not been set
on the Operator image.

rh-shield-operator/Dockerfile

@@ -5,6 +5,7 @@ ARG RELEASE_VERSION
 
 LABEL name="rh-shield-operator" \
       vendor="Sysdig" \
+      maintainer="Sysdig" \
       version="${RELEASE_VERSION}" \
       release="1" \
       summary="Operator based on the shield chart by Sysdig" \