Bump org.jetbrains.kotlin:kotlin-gradle-plugin from 1.9.0 to 2.1.0

Bumps [org.jetbrains.kotlin:kotlin-gradle-plugin](https://github.com/JetBrains/kotlin) from 1.9.0 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@v1.9.0...v2.1.0)

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

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

Author: dependabot[bot]

buildSrc/build.gradle.kts

@@ -27,7 +27,7 @@ dependencies {
     implementation("io.github.gradle-nexus:publish-plugin:1.3.0")
     implementation("net.researchgate:gradle-release:3.0.2")
     implementation("com.github.dpaukov:combinatoricslib3:3.4.0")
-    implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:1.9.0")
+    implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:2.1.0")
     implementation("me.champeau.jmh:jmh-gradle-plugin:0.7.2")
     implementation("se.bjurr.gitchangelog:git-changelog-gradle-plugin:2.1.0") {
         isTransitive = false

buildSrc/src/main/kotlin/io.github.nstdio.http.ext.library-conventions.gradle.kts

@@ -34,7 +34,8 @@ java {
 configurations
   .filter { arrayOf("compileClasspath", "runtimeClasspath").contains(it.name) }
   .forEach {
-    it.exclude("org.jetbrains.kotlin", "kotlin-stdlib-jdk8")
+    it.exclude("org.jetbrains.kotlin")
+    it.exclude("org.jetbrains", "annotations")
   }
 
 tasks.named("compileKotlin") {

buildSrc/src/main/kotlin/io.github.nstdio.http.ext.test-conventions.gradle.kts

@@ -156,7 +156,7 @@ tasks {
 
   withType<KotlinCompile> {
     kotlinOptions {
-      useK2 = true
+      languageVersion = "2.0"
       jvmTarget = JavaVersion.VERSION_11.toString()
     }
   }