[#516] Revert pinning the protobuf version

[hatzlj]

reverts #517,

instead of pinning the protobuf version to a specific version in this repo to avoid issues with users having an earlier version of protobuf-java on their classpath as the one we use for the protobuf-codegen, we mange the protobuf-java version in the Axoniq BOM to pin it for framework users.

relates to #516

see also: https://github.com/AxonIQ/axoniq-framework/pull/560

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}