Problem: slashing fix is not included

[yihuang]

Solution:

• add the fix in a hardfork style

👮🏻👮🏻👮🏻 !!!! REFERENCE THE PROBLEM YOUR ARE SOLVING IN THE PR TITLE AND DESCRIBE YOUR SOLUTION HERE !!!! DO NOT FORGET !!!! 👮🏻👮🏻👮🏻

PR Checklist:

• Have you read the CONTRIBUTING.md?
• Does your PR follow the C4 patch requirements?
• Have you rebased your work on top of the latest master?
• Have you checked your code compiles? (make)
• Have you included tests for any non-trivial functionality?
• Have you checked your code passes the unit tests? (make test)
• Have you checked your code formatting is correct? (go fmt)
• Have you checked your basic code style is fine? (golangci-lint run)
• If you added any dependencies, have you checked they do not contain any known vulnerabilities? (go list -json -m all | nancy sleuth)
• If your changes affect the client infrastructure, have you run the integration test?
• If your changes affect public APIs, does your PR follow the C4 evolution of public contracts?
• If your code changes public APIs, have you incremented the crate version numbers and documented your changes in the CHANGELOG.md?
• If you are contributing for the first time, please read the agreement in CONTRIBUTING.md now and add a comment to this pull request stating that your PR is in accordance with the Developer's Certificate of Origin.

Thank you for your code, it's appreciated! :)

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 33.08%. Comparing base (641d3b9) to head (54a21ba).

❗ Current head 54a21ba differs from pull request most recent head ead1ae4. Consider uploading reports for the commit ead1ae4 to get more accurate results

Files	Patch %	Lines
app/forks.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff               @@
##           release/v4    #1036      +/-   ##
==============================================
+ Coverage       30.08%   33.08%   +3.00%     
==============================================
  Files             125      127       +2     
  Lines           20039    20043       +4     
==============================================
+ Hits             6028     6631     +603     
+ Misses          12965    12351     -614     
- Partials         1046     1061      +15     

Flag	Coverage Δ
integration_tests	20.71% <33.33%> (-0.01%)	⬇️
integration_tests_byzantine	9.66% <33.33%> (-0.01%)	⬇️
integration_tests_gov	10.02% <33.33%> (-0.01%)	⬇️
integration_tests_grpc	10.00% <33.33%> (-0.01%)	⬇️
integration_tests_ibc	24.80% <33.33%> (-0.01%)	⬇️
integration_tests_ledger	9.89% <33.33%> (-0.01%)	⬇️
integration_tests_slow	9.89% <33.33%> (-0.01%)	⬇️
integration_tests_solomachine	9.69% <33.33%> (-0.01%)	⬇️
integration_tests_upgrade	10.00% <33.33%> (-0.01%)	⬇️
unit_tests	10.99% <33.33%> (?)

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[queenybee39]

@