refactor: remove usage of ToDec()

[aljo242]

What does this PR does?

Remove all uses of the sdk.Int.ToDec() function. This function is removed in SDK v0.46.0. Conversion between sdk.Int and sdk.Dec can be done using sdk.NewDecFromInt().

Part of #909

Checklist

These are the criteria that every PR should meet, please check them off as you
review them:

• Include tests
• Respect code style and lint
• Update documentation (*.md) (if needed)

[codecov]

Codecov Report

Merging #910 (8e72dab) into develop (f1ee1a7) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop     #910   +/-   ##
========================================
  Coverage    10.56%   10.57%           
========================================
  Files          327      327           
  Lines        75110    75110           
========================================
+ Hits          7938     7941    +3     
+ Misses       66983    66981    -2     
+ Partials       189      188    -1     

Impacted Files	Coverage Δ
x/claim/types/claim_record.go	100.00% <100.00%> (ø)
x/launch/keeper/genesis_validator.go	100.00% <100.00%> (ø)
x/launch/keeper/validator_set.go	100.00% <100.00%> (ø)
x/participation/keeper/total_allocations.go	100.00% <100.00%> (ø)
x/reward/keeper/reward_distribution.go	80.57% <100.00%> (ø)
x/campaign/simulation/store.go	84.45% <0.00%> (+2.02%)	⬆️

[lumtis]

LGTM