fix test missing migration key

Author: atakavci

tests/StackExchange.Redis.Tests/ClusterTests.cs

@@ -810,6 +810,7 @@ public async Task TestShardedPubsubSubscriberAgainsHashSlotMigration()
         using var conn = Create(allowAdmin: true, keepAlive: 1, connectTimeout: 3000, shared: false);
         Assert.True(conn.IsConnected);
         var db = conn.GetDatabase();
+        db.StringSet("testShardChannel", "testValue");
         Assert.Equal(0, await db.PublishAsync(channel, "noClientReceivesThis"));
         await Task.Delay(50); // let the sub settle (this isn't needed on RESP3, note)
 
@@ -873,6 +874,7 @@ private void MigrateSlotForTestShardChannel(bool rollback)
         IServer? serverWithPort7000 = null;
         IServer? serverWithPort7001 = null;
 
+
         string nodeIdForPort7000 = "780813af558af81518e58e495d63b6e248e80adf";
         string nodeIdForPort7001 = "ea828c6074663c8bd4e705d3e3024d9d1721ef3b";
         foreach (var server in servers)