Barracuda - remove unused private variable (#2128)

UnitySDK/Assets/ML-Agents/Scripts/InferenceBrain/GeneratorImpl.cs

         private int memoriesCount;
         private int memoryIndex;
         
-        public BarracudaRecurrentInputGenerator(int memoriesCount, int memoryIndex)
+        public BarracudaRecurrentInputGenerator(int memoryIndex)
-            this.memoriesCount = memoriesCount;
             this.memoryIndex = memoryIndex;
         }
         

UnitySDK/Assets/ML-Agents/Scripts/InferenceBrain/TensorGenerator.cs

             Barracuda.Model model = (Barracuda.Model) barracudaModel;
             for (var i = 0; i < model?.memories.Length; i++)
             {
-                _dict[model.memories[i].input] = new BarracudaRecurrentInputGenerator(model.memories.Length, i);
+                _dict[model.memories[i].input] = new BarracudaRecurrentInputGenerator(i);
             }
             #endif