Remove unused allocation (#5068)

com.unity.ml-agents/Runtime/Communicator/GrpcExtensions.cs

             if (dimensionPropertySensor != null)
             {
                 var dimensionProperties = dimensionPropertySensor.GetDimensionProperties();
-                int[] intDimensionProperties = new int[dimensionProperties.Length];
                 for (int i = 0; i < dimensionProperties.Length; i++)
                 {
                     observationProto.DimensionProperties.Add((int)dimensionProperties[i]);