Remove upper bound on dlt dependency in Kafka source

[aksestok]

Tell us what you do here

• improving, documenting, or customizing an existing source (please link an issue or describe below)

Short description

Unpin the dlt dependency for the Kafka source.

Related Issues

• Fixes #414

Additional Context

[IlyaFaer]

@rudolfix, most likely I took it from another source, as an example. I guess there will be no problems if we drop the bound.