[RELEASE] [DOCKER] Update the docker file for release 4.7.3

*Motivation*

Update release version in the docker file




Reviewers: Enrico Olivelli <eolivelli@gmail.com>

This closes #1860 from sijie/update_docker_version
diff --git a/docker/Dockerfile b/docker/Dockerfile
index 1d1fc03..1e69998 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -20,7 +20,7 @@
 FROM centos:7
 MAINTAINER Apache BookKeeper <dev@bookkeeper.apache.org>
 
-ARG BK_VERSION=4.7.2
+ARG BK_VERSION=4.7.3
 ARG DISTRO_NAME=bookkeeper-server-${BK_VERSION}-bin
 ARG GPG_KEY=FD74402C