fix to spamming seconds behind

src/main/java/com/imaginarycode/minecraft/redisbungee/RedisBungee.java

@@ -105,6 +105,7 @@ public final class RedisBungee extends Plugin {
                         servers.add(entry.getKey());
                     else if (nag && nagTime <= 0) {
                         getLogger().severe(entry.getKey() + " is " + (time - stamp) + " seconds behind! (Time not synchronized or server down?)");
+                        jedis.hdel("heartbeats",  entry.getKey());
                     }
                 } catch (NumberFormatException ignored) {
                 }