Update Kotlin version to 2.1.21 in samples

Author: Mr3zee

samples/ktor-all-platforms-app/gradle/libs.versions.toml

@@ -1,5 +1,5 @@
 [versions]
-kotlin = "2.1.20"
+kotlin = "2.1.21"
 
 agp = "8.9.1"
 android-compileSdk = "35"

samples/ktor-android-app/gradle/libs.versions.toml

@@ -1,6 +1,6 @@
 [versions]
 agp = "8.9.1"
-kotlin = "2.1.20"
+kotlin = "2.1.21"
 androidx-activityCompose = "1.10.1"
 androidx-appcompat = "1.7.0"
 androidx-constraintlayout = "2.2.1"

samples/ktor-web-app/gradle/libs.versions.toml

@@ -1,5 +1,5 @@
 [versions]
-kotlin = "2.1.20"
+kotlin = "2.1.21"
 kotlin-wrappers-bom = "2025.4.8"
 ktor = "3.1.2"
 kotlinx-serialization-json = "1.8.1"

samples/simple-ktor-app/build.gradle.kts

@@ -3,8 +3,8 @@
  */
 
 plugins {
-    kotlin("jvm") version "2.1.20"
-    kotlin("plugin.serialization") version "2.1.20"
+    kotlin("jvm") version "2.1.21"
+    kotlin("plugin.serialization") version "2.1.21"
     id("io.ktor.plugin") version "3.1.2"
     id("org.jetbrains.kotlinx.rpc.plugin") version "0.7.0"
 }
@@ -40,5 +40,5 @@ dependencies {
     implementation("ch.qos.logback:logback-classic:1.5.18")
 
     testImplementation("io.ktor:ktor-server-test-host")
-    testImplementation("org.jetbrains.kotlin:kotlin-test-junit:2.1.20")
+    testImplementation("org.jetbrains.kotlin:kotlin-test-junit:2.1.21")
 }