[Kotlin] fix #20231, OkHttp client can handle a field with a list of… #1

Job	Run time
Build Kotlin server (jdk8) (samples/server/petstore/kotlin-springboot)	1m 44s
Build Kotlin server (jdk8) (samples/server/petstore/kotlin-springboot-multipart-request-model)	1m 48s
Build Kotlin server (jdk8) (samples/server/petstore/kotlin-springboot-bigdecimal-default)	1m 45s
Build Kotlin server (jdk8) (samples/server/petstore/kotlin-springboot-delegate)	2m 21s
Build Kotlin server (jdk8) (samples/server/petstore/kotlin-springboot-modelMutable)	1m 48s
Build Kotlin server (jdk8) (samples/server/petstore/kotlin-springboot-reactive)	1m 40s
Build Kotlin server (jdk8) (samples/server/petstore/kotlin-springboot-source-swagger1)	1m 44s
Build Kotlin server (jdk8) (samples/server/petstore/kotlin-springboot-source-swagger2)	1m 45s
Build Kotlin server (jdk8) (samples/server/petstore/kotlin-springboot-springfox)	1m 41s
Build Kotlin server (jdk8) (samples/server/petstore/kotlin-server/ktor)	1m 55s
Build Kotlin server (jdk8) (samples/server/petstore/kotlin-server/jaxrs-spec)	1m 30s
Build Kotlin server (jdk8) (samples/server/petstore/kotlin-server/jaxrs-spec-mutiny)	1m 24s
Build Kotlin server (jdk8) (samples/server/petstore/kotlin-server-modelMutable)	1m 47s
Build Kotlin server (jdk8) (samples/server/petstore/kotlin-server/javalin)	1m 39s
Build Kotlin server (jdk8) (samples/server/others/kotlin-server/jaxrs-spec)	1m 25s
Build Kotlin server (jdk8) (samples/server/others/kotlin-server/jaxrs-spec-array-response)	1m 30s
Build Kotlin server (jdk8) (samples/server/petstore/kotlin-spring-cloud)	1m 39s
	29m 5s

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