Unsupported docker image usage in Debezium KStreams Example [DBZ-4593]

Migrated from [DBZ-4593](https://issues.redhat.com/browse/DBZ-4593)

'docker-compose up --build' fails with following error.
{code:bash}
Building aggregator
[+] Building 1.4s (7/7) FINISHED
=> [internal] load build definition from Dockerfile 0.0s
=> => transferring dockerfile: 37B 0.0s
=> [internal] load .dockerignore 0.0s
=> => transferring context: 2B 0.0s
=> ERROR [internal] load metadata for registry.fedoraproject.org/fedora-minimal:29 0.6s
=> CANCELED [internal] load metadata for docker.io/library/fedora:29 1.3s
=> CANCELED [internal] load metadata for docker.io/library/maven:3.5-jdk-8-alpine 1.3s
=> [auth] library/fedora:pull token for registry-1.docker.io 0.0s
=> [auth] library/maven:pull token for registry-1.docker.io 0.0s
------
> [internal] load metadata for registry.fedoraproject.org/fedora-minimal:29:
------
failed to solve with frontend dockerfile.v0: failed to create LLB definition: registry.fedoraproject.org/fedora-minimal:29: not found
ERROR: Service 'aggregator' failed to build : Build failed
{code}
It turns out that registry.fedoraproject.org/fedora-minimal:29 is not supported. A minimum version supported for this image seems like 30 according to [this site|https://registry.fedoraproject.org/repo/fedora-minimal/tags/]

It seems working well after I only change the image tag in [this line|https://github.com/debezium/debezium-examples/blob/944a3bb7b6a9fa31833095cd0ba2fdc9b8027eb4/kstreams/poc-ddd-aggregates/Dockerfile#L31] from 29 to 30.

Open kstreams/poc-ddd-aggregates/Dockerfile at line 31 and inspect the registry.fedoraproject.org/fedora-minimal image reference. Run `docker-compose up --build` for the KStreams example; done means the aggregator image builds without the reported unsupported-image error.

Written by the indexing model from the issue text.