Clean-up InstrEncoder::encode_branch_{nez,eqz} methods

[Robbepop]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 87.90850% with 37 lines in your changes missing coverage. Please review.

Project coverage is 81.64%. Comparing base (bd735a0) to head (8c9c57e).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...rates/wasmi/src/engine/translator/instr_encoder.rs	81.08%	28 Missing ⚠️
crates/wasmi/src/engine/translator/comparator.rs	94.30%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1229      +/-   ##
==========================================
+ Coverage   81.50%   81.64%   +0.13%     
==========================================
  Files         303      304       +1     
  Lines       25008    25111     +103     
==========================================
+ Hits        20384    20501     +117     
+ Misses       4624     4610      -14     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.