Yaml deserializer strictness: disallow key duplicates (#1176)

[YamlDotNet 12.2.1](https://github.com/aaubry/YamlDotNet/releases/tag/v12.2.1) brought in a new yaml strictness check: no duplicate keys

Author: stan-sz

src/KubernetesClient.Models/KubernetesYaml.cs

@@ -25,6 +25,7 @@ public static class KubernetesYaml
                 .WithOverridesFromJsonPropertyAttributes();
         private static readonly IDeserializer StrictDeserializer =
             CommonDeserializerBuilder
+            .WithDuplicateKeyChecking()
             .Build();
         private static readonly IDeserializer Deserializer =
             CommonDeserializerBuilder