Fix imports

src/main/java/com/dmdirc/ui/messages/UnreadStatusManagerImpl.java

 import com.dmdirc.events.DisplayableEvent;
 import com.dmdirc.events.QueryHighlightEvent;
 import com.dmdirc.events.UnreadStatusChangedEvent;
-import com.dmdirc.events.eventbus.EventBus;
 import com.dmdirc.interfaces.WindowModel;
 import com.dmdirc.util.colours.Colour;
-
-import java.util.Optional;
-import java.util.concurrent.TimeUnit;
-
-import io.reactivex.Emitter;
-import io.reactivex.Observable;
-import io.reactivex.ObservableEmitter;
-import io.reactivex.Observer;
-import io.reactivex.functions.Consumer;
 import io.reactivex.subjects.PublishSubject;
-import io.reactivex.subjects.ReplaySubject;
 import io.reactivex.subjects.Subject;
 import net.engio.mbassy.listener.Handler;
-import org.reactivestreams.Publisher;
+
+import java.util.Optional;
+import java.util.concurrent.TimeUnit;
 
 /**
  * Tracks unread messages and other notifications.