Rust unneeded mut tx v1

[catenacyber]

Link to ticket: https://redmine.openinfosecfoundation.org/issues/
None, simple cleanup

Describe changes:

• rust: remove some unneeded mut

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 10 lines in your changes missing coverage. Please review.

Project coverage is 80.62%. Comparing base (078c646) to head (6a19786).
Report is 12 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #12409      +/-   ##
==========================================
- Coverage   80.63%   80.62%   -0.01%     
==========================================
  Files         917      917              
  Lines      258687   258675      -12     
==========================================
- Hits       208601   208568      -33     
- Misses      50086    50107      +21     

Flag	Coverage Δ
fuzzcorpus	56.81% <63.46%> (-0.01%)	⬇️
livemode	19.39% <0.00%> (+<0.01%)	⬆️
pcap	44.26% <23.07%> (+<0.01%)	⬆️
suricata-verify	63.25% <87.50%> (+0.02%)	⬆️
unittests	58.51% <0.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

[jasonish]

Looks OK to me. Using &mut in these places might have been a requirement in a much earlier version of Rust when we established this pattern.

[suricata-qa]

Information: QA ran without warnings.

Pipeline 24237

[victorjulien]

Merged in #12413, thanks!