Fix denom (symbol)

[FrancoCRO]

The parent constructor is run before the child, so denom is not set in DSToken
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Thank you for your code, it's appreciated! :)

[yihuang]

good catch 👍

[codecov]

Codecov Report

Merging #179 (79d06f5) into main (3ea70c5) will increase coverage by 5.11%.
The diff coverage is 54.06%.

@@            Coverage Diff             @@
##             main     #179      +/-   ##
==========================================
+ Coverage   21.51%   26.63%   +5.11%     
==========================================
  Files          27       33       +6     
  Lines        1729     2328     +599     
==========================================
+ Hits          372      620     +248     
- Misses       1324     1662     +338     
- Partials       33       46      +13     

Impacted Files	Coverage Δ
app/prefix.go	0.00% <0.00%> (ø)
app/test_helpers.go	0.00% <0.00%> (ø)
x/cronos/keeper/grpc_query.go	0.00% <0.00%> (ø)
x/cronos/keeper/msg_server.go	5.00% <0.00%> (-1.46%)	⬇️
x/cronos/module.go	59.64% <0.00%> (-2.17%)	⬇️
x/cronos/types/codec.go	0.00% <0.00%> (ø)
x/cronos/types/events.go	0.00% <ø> (ø)
x/cronos/types/messages.go	20.22% <ø> (+20.22%)	⬆️
x/cronos/types/params.go	57.35% <ø> (+3.78%)	⬆️
x/cronos/types/proposal.go	11.11% <ø> (ø)
... and 19 more

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