Support Kotlin 2.2.21

[ganadist]

• Kotlin 2.2.21, the (likely) final version supporting k1, has been released.
• Although KSP version 2.3.0, which only supports K2, has already been released, please consider releasing KSP version 2.2.21-2.0.4 to allow KSP1 to be used with 2.2.21, as there may be developers who wish to keep using KSP1.

[nklomp]

PR: #2671

[ganadist]

https://github.com/google/ksp/releases/tag/2.2.21-2.0.4 was published, and resolved this.