Fix select assign backward

[nathanielsimard]

The select assign backward wasn't right for the RHS

Fix #1727

[codecov]

Codecov Report

Attention: Patch coverage is 85.18519% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 86.55%. Comparing base (0b919b6) to head (d97bb90).
Report is 6 commits behind head on main.

Files	Patch %	Lines
crates/burn-tch/src/ops/base.rs	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1739      +/-   ##
==========================================
+ Coverage   86.47%   86.55%   +0.07%     
==========================================
  Files         698      699       +1     
  Lines       82880    83223     +343     
==========================================
+ Hits        71673    72031     +358     
+ Misses      11207    11192      -15     

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[louisfd]

The change for lhs is actually good, my request is about the lhs. Good job

[louisfd]

LGTM