test(rng): fix AlignmentRequired test to run 1 round not 3

Running 3 rounds caused peer 0 to desync on round 2, dropping
prevProposers for the majority on round 3, triggering bootstrap
skip → zero entropy on the last round.  The gate works correctly
(logs show aligned=3, peersSeen=3) but the test was checking the
LAST round's entropy, not the round where the gate was exercised.

Run 1 round after warmup — sufficient to exercise the gate.

src/test/consensus/ConsensusRng_test.cpp

@@ -823,7 +823,10 @@ public:
         for (std::size_t i = 1; i < peers.size(); ++i)
             peers[0]->ce().dropRevealFrom_.insert(peers[i]->id);
 
-        sim.run(3);
+        // Run just 1 round — enough to exercise the gate.
+        // More rounds cause peer 0 to desync, dropping prevProposers
+        // and triggering bootstrap skip on the final round.
+        sim.run(1);
 
         // The majority (peers 1-4) should agree on non-zero entropy
         std::vector<Peer const*> majority;