refactor(bmr): Clean up bsc and snow chains from unused code (#813)

[andrii-kl]

Closes #813

Checklist:

• [x] I have performed a self-review of my own code
• [x] I have documented my code in accordance with the documentation guidelines
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] I have run the unit tests
• [ ] I only have one commit (if not, squash them into one commit).
• [x] I have a descriptive commit message that adheres to the commit message guidelines

Please review the CONTRIBUTING.md file for detailed contributing guidelines.

[codecov[bot]]

Codecov Report

Merging #814 (541434a) into main (79537e7) will increase coverage by 1.97%. The diff coverage is 45.45%.

@@             Coverage Diff              @@
##               main     #814      +/-   ##
============================================
+ Coverage     38.20%   40.18%   +1.97%     
  Complexity      801      801              
============================================
  Files           115      112       -3     
  Lines         11161    10612     -549     
  Branches        941      941              
============================================
  Hits           4264     4264              
+ Misses         6579     6030     -549     
  Partials        318      318              

Impacted Files	Coverage Δ
cmd/iconbridge/chain/bsc/sender.go	38.70% <ø> (ø)
cmd/iconbridge/chain/icon/client.go	28.30% <ø> (+2.87%)	:arrow_up:
cmd/iconbridge/chain/substrate-eth/client.go	0.00% <0.00%> (ø)
cmd/iconbridge/chain/substrate-eth/receiver.go	0.00% <0.00%> (ø)
cmd/iconbridge/chain/substrate-eth/sender.go	0.00% <0.00%> (ø)
cmd/iconbridge/chain/bsc/receiver.go	59.02% <100.00%> (ø)
...d/iconbridge/chain/substrate-eth/abi/bmc_abigen.go