upgrade: set val min commission

[javiersuweijie]

Enforce min commission rate to be 5% based on the proposal that was passed: https://station.terra.money/proposal/phoenix-1/4803

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.63%. Comparing base (06d1d00) to head (0cb2b42).
Report is 4 commits behind head on release/v2.10.

Additional details and impacted files

@@                Coverage Diff                @@
##           release/v2.10     #268      +/-   ##
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+ Coverage          70.50%   70.63%   +0.12%     
=================================================
  Files                 45       45              
  Lines               2092     2101       +9     
=================================================
+ Hits                1475     1484       +9     
  Misses               451      451              
  Partials             166      166              

Files	Coverage Δ
app/upgrade_handler.go	80.19% <100.00%> (+1.93%)	⬆️