Add BusGroup#unregister(EventListener) for single listeners

src/main/java/net/minecraftforge/eventbus/api/bus/BusGroup.java

@@ -89,4 +89,11 @@ static BusGroup create(String name, Class<?> baseType) {
      *                  {@link #register(MethodHandles.Lookup, Class)} or {@link #register(MethodHandles.Lookup, Object)}
      */
     void unregister(Collection<EventListener> listeners);
+
+    /**
+     * Unregisters the given listener from this BusGroup.
+     * @param listeners The listeners to unregister, contained from the collection obtained from
+     *                  {@link #register(MethodHandles.Lookup, Class)} or {@link #register(MethodHandles.Lookup, Object)}
+     */
+    void unregister(EventListener listeners);
 }

src/main/java/net/minecraftforge/eventbus/internal/BusGroupImpl.java

@@ -79,10 +79,15 @@ public void unregister(Collection<EventListener> listeners) {
                     "the BusGroup#register method.");
 
         for (var listener : listeners) {
-            getOrCreateEventBus((Class<? extends Event>) listener.eventType()).removeListener(listener);
+            unregister(listener);
         }
     }
 
+    @Override
+    public void unregister(EventListener listener) {
+        getOrCreateEventBus((Class<? extends Event>) listener.eventType()).removeListener(listener);
+    }
+
     //region Internal access only
     @SuppressWarnings("unchecked")
     private <T extends Event> EventBus<T> createEventBus(Class<T> eventType) {