Cancel legacy Java SDK client api-client

[arielshaqed]

What

1. Publish the next release of io.lakefs:api-client with a changed
   description. Instead of "lakeFS OpenAPI Java client legacy SDK", state
   "[EOL] Do NOT use: lakeFS OpenAPI Java client legacy SDK".
2. Remove support from the lakeFS and stop publishing new versions of
   io.lakefs:api-client.

Why

This is the pre-1.0 Java SDK. It shows very low usage. Indeed, the code
migration guide mistakenly says that this is the
io.lakefs:lakefs-client package. In fact it is io.lakefs:api-client.
We have seen no complaints even about this.

Supporting this legacy implementation requires some real work. In
particular, we do not want to upgrade the OpenAPI release we use to build
this client, and it has occasional low-threat CVEs. I would rather dedicate
this work to tasks that bring real value to users and to customers.