Bump multiplatform from 2.0.20 to 2.0.21

Bumps [multiplatform](https://github.com/JetBrains/kotlin) from 2.0.20 to 2.0.21.
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/v2.0.21/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.0.20...v2.0.21)

---
updated-dependencies:
- dependency-name: multiplatform
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

build.gradle.kts

@@ -7,7 +7,7 @@ import org.jetbrains.kotlin.gradle.targets.js.dsl.ExperimentalWasmDsl
 import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
 plugins {
-    kotlin("multiplatform") version "2.0.20"
+    kotlin("multiplatform") version "2.0.21"
     // This version is dependent on the maximum tested version
     // of this plugin within the Kotlin multiplatform library
     id("com.android.library") version "8.6.1"