[hotfix] [docs] Use FROM ververica/flink-statefun

As far as I can tell, flink-statefun is only available under ververica in
DockerHub.

Author: Ufuk Celebi

docs/deployment-and-operations/packaging.md

@@ -38,7 +38,7 @@ The provided base image allows teams to package their applications with all the
 Below is an example Dockerfile for building a Stateful Functions image with both an [embedded module]({{ site.baseurl }}/sdk/modules.html#embedded-module) and a [remote module]({{ site.baseurl }}/sdk/modules.html#remote-module) for an application called ``statefun-example``.
 
 {% highlight dockerfile %}
-FROM flink-statefun:{{ site.version }}
+FROM ververica/flink-statefun:{{ site.version }}
 
 RUN mkdir -p /opt/statefun/modules/statefun-example
 RUN mkdir -p /opt/statefun/modules/remote

docs/getting-started/python_walkthrough.md

@@ -338,7 +338,7 @@ The base image provides the Stateful Function runtime, it will use the provided
 This can be found in the `Dockerfile` in the root directory. 
 
 {% highlight docker %}
-FROM flink-statefun:{{ site.version }}
+FROM ververica/flink-statefun:{{ site.version }}
 
 RUN mkdir -p /opt/statefun/modules/greeter
 ADD module.yaml /opt/statefun/modules/greeter