[kotlin-spring] Fix gradle build failure when generated with interfaceOnly=true (#18809)

* Fix kotlin-spring not building when `interfaceOnly=true`

Fixes #18803

* Regenerate fixed kotlin-spring samples

* Include sample kotlin-springboot-request-cookie in CI build check

* Apply suggestions from code review

Co-authored-by: Stefan Koppier <stefan.koppier@outlook.com>

---------

Co-authored-by: Stefan Koppier <stefan.koppier@outlook.com>

samples/server/petstore/kotlin-springboot-request-cookie/build.gradle.kts

@@ -13,6 +13,10 @@ tasks.withType<KotlinCompile> {
     kotlinOptions.jvmTarget = "17"
 }
 
+tasks.bootJar {
+    enabled = false
+}
+
 plugins {
     val kotlinVersion = "1.7.10"
     id("org.jetbrains.kotlin.jvm") version kotlinVersion