feat: do not deduct tax in ibc token

[JoowonYun]

Summary of changes

The policy has been changed to not deduct tax for IBC tokens.

Report of required housekeeping

• Github issue OR spec proposal link
• Wrote tests
• Added a relevant changelog entry to CHANGELOG.md

---

(FOR ADMIN) Before merging

• Added appropriate labels to PR
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)
• Confirm added tests are consistent with the intended behavior of changes
• Ensure all tests pass

[codecov-commenter]

Codecov Report

Merging #16 (dd35a13) into main (7839ad1) will decrease coverage by 0.18%.
The diff coverage is 74.07%.

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@@            Coverage Diff             @@
##             main      #16      +/-   ##
==========================================
- Coverage   89.01%   88.83%   -0.18%     
==========================================
  Files          19       19              
  Lines        3668     3699      +31     
==========================================
+ Hits         3265     3286      +21     
- Misses        403      413      +10     

Files	Coverage Δ
contracts/terraswap_pair/src/contract.rs	93.78% <ø> (+0.04%)	⬆️
packages/classic_terraswap/src/testing.rs	100.00% <100.00%> (ø)
contracts/terraswap_router/src/contract.rs	84.71% <0.00%> (-0.14%)	⬇️
contracts/terraswap_router/src/querier.rs	90.47% <50.00%> (-9.53%)	⬇️
packages/classic_terraswap/src/asset.rs	93.58% <83.33%> (-0.94%)	⬇️
packages/classic_terraswap/src/mock_querier.rs	87.90% <33.33%> (+1.05%)	⬆️

... and 7 files with indirect coverage changes

[jbamlee]

Question.
Does IBC token have only A-F characters?

[JoowonYun]

Question. Does IBC token have only A-F characters?

IBC hash is SHA256. So, it is a 64-digit hexadecimal hex value.