Remove is_chunk_producer_for_epoch from EpochManagerAdapter

[pugachAG]

It was introduced in #10633 to handle the following error:

2.098s ERROR handle{handler="ApplyChunksDoneMessage" actor="ClientActor"}:try_process_unfinished_blocks:postprocess_ready_blocks{should_produce_chunk=true}:on_block
_accepted_with_optional_chunk_produce{block_hash=61NPprDM6Q1tTiMscXVC3QcWribUP72idpF6ju5jqJwb status=Next provenance=PRODUCED skip_produce_chunk=false is_syncing=fal
se sync_status=NoSync}:produce_chunks{validator_id=AccountId("test1") block_height=20}:on_block_accepted{prev_block_hash=61NPprDM6Q1tTiMscXVC3QcWribUP72idpF6ju5jqJwb
 shard_id=0}: client: Failed to send chunk state witness to chunk validators err=Other("Missing implicit transition state proof for block 3VKaWmmgDcaSwszEWuzcf2o9vXR
s4TuLoPhwWzCA2Lbu and shard 0")                                                        

This is caused by should_produce_state_witness_for_this_or_next_epoch returning false for the chunk producer due to MockEpochManager::get_epoch_chunk_producers returning an empty Vec.

Blocked by removal of MockEpochManager: #10634