remove misbehaviour GetHeight

[colin-axner]

Description

closes: #148

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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-commenter]

Codecov Report

Merging #166 (f245118) into main (5991e86) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #166   +/-   ##
=======================================
  Coverage   79.90%   79.91%           
=======================================
  Files         107      107           
  Lines        6420     6417    -3     
=======================================
- Hits         5130     5128    -2     
+ Misses        932      931    -1     
  Partials      358      358           

Impacted Files	Coverage Δ
modules/core/keeper/msg_server.go	65.08% <ø> (+0.19%)	⬆️
...light-clients/06-solomachine/types/misbehaviour.go	96.00% <ø> (-0.16%)	⬇️
.../light-clients/07-tendermint/types/misbehaviour.go	71.66% <ø> (-0.47%)	⬇️
modules/core/02-client/keeper/client.go	98.56% <100.00%> (ø)