Bump org.jetbrains.kotlin.jvm from 2.3.20 to 2.3.21

Bumps org.jetbrains.kotlin.jvm from 2.3.20 to 2.3.21.

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin.jvm
  dependency-version: 2.3.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -1,5 +1,5 @@
 [plugins]
-kotlin = { id = "org.jetbrains.kotlin.jvm", version = "2.3.20" }
+kotlin = { id = "org.jetbrains.kotlin.jvm", version = "2.3.21" }
 dokka-base  = { id = "org.jetbrains.dokka", version = "2.2.0" }
 dokka-java  = { id = "org.jetbrains.dokka-javadoc", version = "2.2.0" }