Update SqlMapperExtensions.Async.cs

Made the same fix to `InsertAsync`

Dapper.Contrib/SqlMapperExtensions.Async.cs

@@ -165,7 +165,7 @@ public static partial class SqlMapperExtensions
             var name = GetTableName(type);
             var sbColumnList = new StringBuilder(null);
             var allProperties = TypePropertiesCache(type);
-            var keyProperties = KeyPropertiesCache(type);
+            var keyProperties = KeyPropertiesCache(type).ToList();
             var computedProperties = ComputedPropertiesCache(type);
             var allPropertiesExceptKeyAndComputed = allProperties.Except(keyProperties.Union(computedProperties)).ToList();