Write out the corresponding DateTime value as a short date representation by retrieving a substring of the instance

Author: MaggieKimani1

src/Microsoft.OpenApi/Any/OpenApiPrimitive.cs

@@ -118,7 +118,7 @@ public void Write(IOpenApiWriter writer, OpenApiSpecVersion specVersion)
 
                 case PrimitiveType.Date:
                     var dateValue = (OpenApiDate)(IOpenApiPrimitive)this;
-                    writer.WriteValue(dateValue.Value);
+                    writer.WriteValue(dateValue.Value.ToString("o").Substring(0, 10));
                     break;
 
                 case PrimitiveType.DateTime: