reverted GroundTruthPasses back to the internal interface

com.unity.perception/Runtime/GroundTruth/RenderPasses/CrossPipelinePasses/GroundTruthCrossPipelinePass.cs

 
 namespace UnityEngine.Perception.GroundTruth
 {
-    public abstract class GroundTruthCrossPipelinePass : IGroundTruthGenerator
+    abstract class GroundTruthCrossPipelinePass : IGroundTruthGenerator
     {
         public Camera targetCamera;
 

com.unity.perception/Runtime/GroundTruth/RenderPasses/HdrpPasses/GroundTruthPass.cs

 
 namespace UnityEngine.Perception.GroundTruth
 {
-    public abstract class GroundTruthPass : CustomPass, IGroundTruthGenerator
+    abstract class GroundTruthPass : CustomPass, IGroundTruthGenerator
     {
         public Camera targetCamera;
 
         {
             if (!m_IsActivated)
             {
-                LabeledObjectsManager.singleton.Activate(this);
+                LabelManager.singleton.Activate(this);
                 m_IsActivated = true;
             }
         }
-            LabeledObjectsManager.singleton.Deactivate(this);
+            LabelManager.singleton.Deactivate(this);
         }
     }
 }