chore(deps): update plugin org.jetbrains.kotlin.plugin.spring to v2.1.21 (#477)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

build.gradle.kts

@@ -4,7 +4,7 @@ import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 plugins {
     java
     kotlin("jvm") version "1.9.25"
-    kotlin("plugin.spring") version "2.1.20"
+    kotlin("plugin.spring") version "2.1.21"
     id("com.github.johnrengelman.shadow") version "8.1.1"
     id("org.jlleitschuh.gradle.ktlint") version "12.2.0"
     id("org.jetbrains.gradle.plugin.idea-ext") version "1.1.10"