Update kotlin monorepo to v2.0.21

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
org.jetbrains.kotlin.plugin.serialization (source)	2.0.20 -> 2.0.21
org.jetbrains.kotlin:kotlin-gradle-plugin (source)	2.0.20 -> 2.0.21

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Configuration

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[github-actions]

Apk size:

Aar size change: +0.0B (84.5KiB -> 84.5KiB)

Diffuse output:

OLD: diffuse-source-file-release
NEW: screenshot-testing-core-release.aar

 AAR      │ old      │ new      │ diff 
──────────┼──────────┼──────────┼──────
      jar │ 92.2 KiB │ 92.2 KiB │  0 B 
 manifest │    227 B │    227 B │  0 B 
    other │    156 B │    156 B │  0 B 
──────────┼──────────┼──────────┼──────
    total │ 92.6 KiB │ 92.6 KiB │  0 B 

 JAR     │ old │ new │ diff      
─────────┼─────┼─────┼───────────
 classes │  44 │  44 │ 0 (+0 -0) 
 methods │ 577 │ 577 │ 0 (+0 -0) 
  fields │ 159 │ 159 │ 0 (+0 -0)