Update sdks.yaml

Author: rlhagerm

aws_doc_sdk_examples_tools/config/sdks.yaml

@@ -236,7 +236,7 @@ Kotlin:
       expanded:
         long: "AWS SDK for .NET (v4)"
         short: "SDK for .NET (v4)"
-      guide: "sdk-for-net/v3/developer-guide/welcome.html"
+      guide: "sdk-for-net/v4/developer-guide/welcome.html"
       api_ref:
         uid: "DotNetSDKV4"
         name: "&guide-net-api;"