fix: remove unnecessary permutedims in batched_mul

[avik-pal]

No description provided.

[avik-pal]

With the new jll these messages are showing up:

I0000 00:00:1756739042.027890   27528 dump.cc:108] [MaybeDumpCompileInputs] Dumping PJRT inputs for module: reactant_batched...
I0000 00:00:1756739042.027925   27528 dump.cc:120]   Dump path not set via xla_dump_to, skipping dump.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 42.57%. Comparing base (d211dd6) to head (301ed86).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1612      +/-   ##
==========================================
- Coverage   42.61%   42.57%   -0.04%     
==========================================
  Files         123      123              
  Lines       21822    21816       -6     
==========================================
- Hits         9300     9289      -11     
- Misses      12522    12527       +5     

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

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.