feat: remove support for named sharding (setting pubsub topic manually)

[adklempner]

This is a feature or change request

Problem

With #1751 , named sharding will be deprecated. We continue to allow setting the pubsub topic manually to prevent breaking changes and give users time to transition to static or auto sharding. Eventually this needs to be completely removed.

Proposed Solutions

Once all relevant documentation and examples are updated, and we verify that major stakeholders have transitioned away from named sharding, remove all instances of pubsubTopic that were marked as deprecated and update any functions accordingly.

Notes

[adklempner]

Moving to icebox. As of now, Status is continuing to use named sharding for the near future so we should not remove it.

[chair28980]

Item removed from Epic 1.2: https://github.com/waku-org/pm/issues/65