Removal of the ProveCommitAggregate method from the miner actor

[rvagg]

I'm proposing the removal of the ProveCommitAggregate method (Method 26) from the miner actor.

This method has been effectively (not technically) deprecated since the introduction of ProveCommitSectors3, which provides the same functionality with greater flexibility and likely cheaper gas for equivalent use across the various usage scenarios.

As of right now, on-chain analysis shows that the last ProveCommitAggregate messages were processed in July 2024 at epoch 4101201:

• bafy2bzaceag3rvlh6riqg2gekn7hpo6nlrhzjv3pd6l5o66eyvdaqgastac3c
• bafy2bzaceblg5r76wcng44ubjkvrqsfw2dk7g5iygc2kezeas5jp7cuvt65wi

The proposed removal would help reduce technical debt and simplify the protocol without impacting current operations, as all functionality is already covered by ProveCommitSectors3.

Proposed FIP content: #1117

[anorth]

Sounds good to me!