feat(minor-interchain-token-service): make decimals non optional

[cjcobb23]

• all TokenInstance's now have decimals, since DeployTokenManager is no longer supported

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.60%. Comparing base (9150d87) to head (2bbd16f).

Additional details and impacted files

@@                                    Coverage Diff                                     @@
##           refactor/interchain_token_service_message_interceptors     #684      +/-   ##
==========================================================================================
+ Coverage                                                   93.59%   93.60%   +0.01%     
==========================================================================================
  Files                                                         238      238              
  Lines                                                       35437    35430       -7     
==========================================================================================
- Hits                                                        33166    33163       -3     
+ Misses                                                       2271     2267       -4     

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