Skip evm antehandler on non-secp signatures

[philipsu522]

Describe your changes and provide context

EVM antehandler is failing for legacy sr25519 signatures. Specifically, pk, err := btcec.ParsePubKey(acc.GetPubKey().Bytes(), btcec.S256()) fails when the len is unexpected, which is generally the case for non-secp256k1 signatures. Because this antehandler is just associating addresses, we can silently ignore

Testing performed to validate your change

Deployed and verified errors are gone:

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.03%. Comparing base (28c621d) to head (419b947).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1606      +/-   ##
==========================================
- Coverage   61.11%   61.03%   -0.08%     
==========================================
  Files         365      365              
  Lines       26104    26104              
==========================================
- Hits        15953    15933      -20     
- Misses       9148     9167      +19     
- Partials     1003     1004       +1     

Files	Coverage Δ
x/evm/ante/preprocess.go	77.69% <100.00%> (ø)

... and 3 files with indirect coverage changes