Cycles: Cleanup, remove unused method declaration

Was never defined. If it's really needed, consider using `const string&`.

intern/cycles/blender/blender_session.h

@@ -169,9 +169,6 @@ protected:
 
 	/* Update tile manager to reflect resumable render settings. */
 	void update_resumable_tile_manager(int num_samples);
-
-	/* Add metadata for cryptomatte layers to the render result. */
-	void add_cryptomatte_metadata(string layer_prefix);
 };
 
 CCL_NAMESPACE_END