undo flushing witness data on shutdown

This fixes wallet_anchorfork.py CI failure, but a separate PR
will restore flushing witness data on shutdown while also
fixing DecrementNoteWitnesses() to not assert when
nd->witnessHeight < indexHeight, which can happen when the
node reorgs upon restart (which this test causes to happen).

src/init.cpp

@@ -229,9 +229,6 @@ void Shutdown()
         if (pcoinsTip != NULL) {
             FlushStateToDisk();
         }
-        // Flush the wallet witness cache to disk (no longer done by FlushStateToDisk())
-        GetMainSignals().SetBestChain(chainActive.GetLocator());
-
         delete pcoinsTip;
         pcoinsTip = NULL;
         delete pcoinscatcher;