x/slashing: remove alias.go usage

[dauTT]

Description

This PR closes a sub task in #6311

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Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

[codecov]

Codecov Report

Merging #6417 into master will not change coverage.
The diff coverage is 81.48%.

@@           Coverage Diff           @@
##           master    #6417   +/-   ##
=======================================
  Coverage   55.66%   55.66%           
=======================================
  Files         465      465           
  Lines       27674    27674           
=======================================
  Hits        15404    15404           
  Misses      11169    11169           
  Partials     1101     1101