Update Kotlin metadata to 2.3.21 for Kotlin 2.4 support

[3flex]

Fixes #1661

[3flex]

Looks like this will be covered in #1664

[ljacomet]

Assuming #1719 lands, this could be merged as-is without impact Gradle compatibility.

[jolaf]

This is not actually working for Kotlin 2.4 support, the plugin is unusable in Kotlin 2.4 setting:

Execution failed for task ':explodeJarTest' (registered by plugin 'com.autonomousapps.dependency-analysis').
> A failure occurred while executing com.autonomousapps.tasks.ExplodeJarTask$ExplodeJarWorkAction
   > Provided Metadata instance has version 2.4.0, while maximum supported version is 2.3.0. To support newer versions, update the kotlin-metadata-jvm library.

[ianbrandt]

#1719 landed. 🎉