test(moa): drop the docstring added to the new layer-attribution test

The zero-comments rule for this branch covers new docstrings as well as
inline comments; the test name already states what it checks.

Author: ayaangazali

tests/structs/test_moa.py

@@ -489,7 +489,6 @@ def test_team_roster_does_not_reach_aggregator_as_user_prose():
 
 
 def test_aggregator_can_tell_which_layer_produced_each_answer():
-    """With layers > 1 each contribution carries the round that produced it."""
     agents, _ = _recording_agents(["W1", "W2"])
     aggregator, agg_calls = _recording_agents(["Agg"])