Do not clone ImageProperties

We're using a structure that is already copied with two immutable values

src/ImageSharp/MetaData/ImageMetaData.cs

@@ -53,7 +53,7 @@ namespace SixLabors.ImageSharp.MetaData
 
             foreach (ImageProperty property in other.Properties)
             {
-                this.Properties.Add(new ImageProperty(property));
+                this.Properties.Add(property);
             }
 
             this.ExifProfile = other.ExifProfile != null
@@ -114,7 +114,6 @@ namespace SixLabors.ImageSharp.MetaData
         /// <summary>
         /// Gets the list of properties for storing meta information about this image.
         /// </summary>
-        /// <value>A list of image properties.</value>
         public IList<ImageProperty> Properties { get; } = new List<ImageProperty>();
 
         /// <summary>

src/ImageSharp/MetaData/ImageProperty.cs

@@ -25,21 +25,6 @@ namespace SixLabors.ImageSharp.MetaData
             this.Value = value;
         }
 
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ImageProperty"/> struct
-        /// by making a copy from another property.
-        /// </summary>
-        /// <param name="other">
-        /// The other <see cref="ImageProperty"/> to create this instance from.
-        /// </param>
-        internal ImageProperty(ImageProperty other)
-        {
-            DebugGuard.NotNull(other, nameof(other));
-
-            this.Name = other.Name;
-            this.Value = other.Value;
-        }
-
         /// <summary>
         /// Gets the name of this <see cref="ImageProperty"/> indicating which kind of
         /// information this property stores.