p2p-governor: Fix prop_governor_target_known_1_valid_subset

The environmentAllKnownPeers should not have been using Signal.stable.
This combinator picks the last value wihtin a time, but in this case
that's inappropriate since it messes with causality. We can and must
check this property for every change in order. Delaying updates until
they are stable means we miss updates and in this case it causes an
untrue property violation.

ouroboros-network/test/Test/Ouroboros/Network/PeerSelection.hs

@@ -793,7 +793,10 @@ prop_governor_target_known_1_valid_subset env =
         validState knownPeersEnv knownPeersGov =
           knownPeersGov `Set.isSubsetOf` knownPeersEnv
 
-     in signalProperty 20 show (uncurry validState) $
+     in counterexample
+          "Signal key: (environment known peers, governor known peers)" $
+
+        signalProperty 20 show (uncurry validState) $
           (,) <$> envKnownPeersSig
               <*> govKnownPeersSig
 
@@ -816,8 +819,7 @@ environmentAllKnownPeers :: Set PeerAddr
                          -> Signal (Set PeerAddr)
 environmentAllKnownPeers localRootPeers =
   --TODO: implement this as a generic signalScanl style combinator
-    Signal.stable
-  . Signal.fromChangeEvents localRootPeers
+    Signal.fromChangeEvents localRootPeers
   . Signal.primitiveTransformEvents (go localRootPeers)
   where
     go :: Set PeerAddr -> [E TraceMockEnv] -> [E (Set PeerAddr)]