fix: Kotlin Version Down To 2.2.21

[xeounxzxu]

Problem

Currently, CodeQL does not support Kotlin version 2.3.0.
(See login below.)

It also appears that the Kotlin version update was caused by a bot, not an intended Kotlin version update.

Error:  Failed to execute goal org.jetbrains.kotlin:kotlin-maven-plugin:2.3.0:compile (compile) on project querydsl-kotlin-codegen: Compilation failure -> [Help 1]
Error:  
Error:  To see the full stack trace of the errors, re-run Maven with the -e switch.
Error:  Re-run Maven using the -X switch to enable full debug logging.
Error:  
Error:  For more information about the errors and possible solutions, please read the following articles:
Error:  [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException
Error:  
Error:  After correcting the problems, you can resume the build with the command
Error:    mvn <args> -rf :querydsl-kotlin-codegen
Error: Process completed with exit code 1.

https://github.com/OpenFeign/querydsl/actions/runs/20293086393/job/58281207169

Solution

We recommend that you lower the version again and run the project as before.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 0.00%. Comparing base (dd8ab54) to head (a186858).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #1531    +/-   ##
=======================================
  Coverage    0.00%   0.00%            
=======================================
  Files         813     838    +25     
  Lines       31466   31795   +329     
  Branches     3614    3622     +8     
=======================================
- Misses      31466   31795   +329     

Flag	Coverage Δ
cubrid	0.00% <ø> (?)
db2	0.00% <ø> (?)
embedded	0.00% <ø> (?)
examples	0.00% <ø> (?)
firebird	0.00% <ø> (?)
mongodb	0.00% <ø> (?)
mysql	0.00% <ø> (?)
oracle	0.00% <ø> (?)
postgresql	0.00% <ø> (?)
test	0.00% <ø> (ø)

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[xeounxzxu]

@velo Can you check the PR?