Update TimeWindow.cs

see https://developer-docs.shipping.amazon.com/apis/docs/shipping-api-v2-reference#timewindow

it's start & end, not startTime and endTime

From actual response:
 "promise": {
          "deliveryWindow": {
            "end": "2025-10-19T06:59:59Z",
            "start": "2025-10-19T06:59:59Z"
          },
          "pickupWindow": {
            "end": null,
            "start": null
          }

Author: cpfk

Source/FikaAmazonAPI/AmazonSpApiSDK/Models/ShippingV2/TimeWindow.cs

@@ -16,16 +16,16 @@ public class TimeWindow {
     /// The start time of the time window.
     /// </summary>
     /// <value>The start time of the time window.</value>
-    [DataMember(Name="startTime", EmitDefaultValue=false)]
-    [JsonProperty(PropertyName = "startTime")]
+    [DataMember(Name="start", EmitDefaultValue=false)]
+    [JsonProperty(PropertyName = "start")]
     public DateTime? StartTime { get; set; }
 
     /// <summary>
     /// The end time of the time window.
     /// </summary>
     /// <value>The end time of the time window.</value>
-    [DataMember(Name="endTime", EmitDefaultValue=false)]
-    [JsonProperty(PropertyName = "endTime")]
+    [DataMember(Name="end", EmitDefaultValue=false)]
+    [JsonProperty(PropertyName = "end")]
     public DateTime? EndTime { get; set; }