Bump kotlinVersion from 2.0.10 to 2.1.0 in /buildSrc

Bumps `kotlinVersion` from 2.0.10 to 2.1.0.

Updates `org.jetbrains.kotlin:kotlin-gradle-plugin` from 2.0.10 to 2.1.0
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.0.10...v2.1.0)

Updates `org.jetbrains.kotlin:kotlin-allopen` from 2.0.10 to 2.1.0
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.0.10...v2.1.0)

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin:kotlin-gradle-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.jetbrains.kotlin:kotlin-allopen
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

buildSrc/build.gradle.kts

@@ -7,7 +7,7 @@ repositories {
 }
 
 dependencies {
-    val kotlinVersion = "2.0.10"
+    val kotlinVersion = "2.1.0"
     implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion")              // kotlin("jvm")
     implementation("org.jetbrains.kotlin:kotlin-allopen:$kotlinVersion")                    // kotlin("plugin.spring")
     implementation("org.springframework.boot:spring-boot-gradle-plugin:3.4.1")      // id("org.springframework.boot")