samples(kotlin): adding the new folder to the github workflow

Author: nikile1123

.github/workflows/samples-kotlin-client.yaml

@@ -70,6 +70,7 @@ jobs:
           - samples/client/others/kotlin-jvm-okhttp-path-comments
           - samples/client/others/kotlin-integer-enum
           - samples/client/petstore/kotlin-allOff-discriminator-kotlinx-serialization
+          - samples/client/petstore/kotlin-generateModelBuilders
     steps:
       - uses: actions/checkout@v5
       - uses: actions/setup-java@v4