fix(deps): update kotlin monorepo to v2.1.21

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
org.jetbrains.kotlin:kotlin-stdlib-jdk8 (source)	2.1.20 -> 2.1.21
org.jetbrains.kotlin:kotlin-gradle-plugin (source)	2.1.20 -> 2.1.21

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[github-actions]

SpotBugs

Category	Base	New
Bad practice	35	35
Correctness	34	34
Dodgy code	26	26
Internationalization	6	6
Malicious code vulnerability	49	49
Multithreaded correctness	3	3
Performance	8	8
Total	161	161

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 43.22%. Comparing base (9e3c004) to head (d8d8fe7).
Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1726      +/-   ##
============================================
+ Coverage     42.88%   43.22%   +0.34%     
- Complexity      973      982       +9     
============================================
  Files           229      229              
  Lines          8490     8490              
  Branches       1109     1109              
============================================
+ Hits           3641     3670      +29     
+ Misses         4346     4316      -30     
- Partials        503      504       +1     

see 5 files with indirect coverage changes

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