test: x/airdrop types

[aljo242]

Basic msg tests

[codecov-commenter]

Codecov Report

Merging #421 (d41523b) into develop (d24c6bc) will increase coverage by 0.25%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop     #421      +/-   ##
===========================================
+ Coverage    54.20%   54.45%   +0.25%     
===========================================
  Files          163      163              
  Lines        11977    11977              
===========================================
+ Hits          6492     6522      +30     
+ Misses        4993     4968      -25     
+ Partials       492      487       -5     

Flag	Coverage Δ
unittests	54.45% <ø> (+0.25%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
x/airdrop/types/genesis.go	45.76% <ø> (+10.16%)	⬆️

... and 2 files with indirect coverage changes

[ajansari95]

lgtm