fix: typo in ValidateGenesis error message

[sunnya97]

Description

closes: #XXXX

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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
• Review Codecov Report in the comment section below once CI passes

[codecov]

Codecov Report

Merging #9422 (c743dc0) into master (d7c5bc5) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master    #9422   +/-   ##
=======================================
  Coverage   60.41%   60.41%           
=======================================
  Files         589      589           
  Lines       37107    37107           
=======================================
  Hits        22417    22417           
  Misses      12712    12712           
  Partials     1978     1978           

Impacted Files	Coverage Δ
x/slashing/types/genesis.go	0.00% <0.00%> (ø)