remove pulsar-standalone image (apache#11657)

### Motivation

Currently, the pulsar-dashboard has been removed in apache#11284, as the pulsar-standalone image is required pulsar-dashboard and provide dashboard service in one container, which leads to building failure in pulsar-standalone image.

in apache#11623, as @merlimat suggests, this PR removes the pulsar-standalone image from master. 

I did a quick search in the codebase to find if there is any doc related to pulsar-standalone image but seems no doc related to pulsar-standalone image anymore. so this PR will not include any doc changes.

### Modifications

- remove pulsar-standalone image

docker/build.sh

@@ -21,5 +21,4 @@
 ROOT_DIR=$(git rev-parse --show-toplevel)
 cd $ROOT_DIR/docker
 
-mvn -f ../dashboard/pom.xml package -Pdocker,-main
 mvn package -Pdocker,-main

docker/pom.xml

@@ -60,7 +60,6 @@
         <module>pulsar</module>
         <module>grafana</module>
         <module>pulsar-all</module>
-        <module>pulsar-standalone</module>
       </modules>
     </profile>
   </profiles>

docker/publish.sh

@@ -65,21 +65,17 @@ set -e
 docker tag pulsar:latest ${docker_registry_org}/pulsar:latest
 docker tag pulsar-all:latest ${docker_registry_org}/pulsar-all:latest
 docker tag pulsar-grafana:latest ${docker_registry_org}/pulsar-grafana:latest
-docker tag pulsar-standalone:latest ${docker_registry_org}/pulsar-standalone:latest
 
 docker tag pulsar:latest ${docker_registry_org}/pulsar:$MVN_VERSION
 docker tag pulsar-all:latest ${docker_registry_org}/pulsar-all:$MVN_VERSION
 docker tag pulsar-grafana:latest ${docker_registry_org}/pulsar-grafana:$MVN_VERSION
-docker tag pulsar-standalone:latest ${docker_registry_org}/pulsar-standalone:$MVN_VERSION
 
 # Push all images and tags
 docker push ${docker_registry_org}/pulsar:latest
 docker push ${docker_registry_org}/pulsar-all:latest
 docker push ${docker_registry_org}/pulsar-grafana:latest
-docker push ${docker_registry_org}/pulsar-standalone:latest
 docker push ${docker_registry_org}/pulsar:$MVN_VERSION
 docker push ${docker_registry_org}/pulsar-all:$MVN_VERSION
 docker push ${docker_registry_org}/pulsar-grafana:$MVN_VERSION
-docker push ${docker_registry_org}/pulsar-standalone:$MVN_VERSION
 
 echo "Finished pushing images to ${docker_registry_org}"