fix: Fix scalar literals

[ritchie46]

fixes #18686

[codecov]

Codecov Report

Attention: Patch coverage is 89.65517% with 3 lines in your changes missing coverage. Please review.

Project coverage is 79.91%. Comparing base (79b91c3) to head (cf5b4b3).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-core/src/scalar/mod.rs	0.00%	1 Missing ⚠️
crates/polars-plan/src/plans/lit.rs	83.33%	1 Missing ⚠️
.../polars-python/src/lazyframe/visitor/expr_nodes.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18707      +/-   ##
==========================================
- Coverage   79.92%   79.91%   -0.02%     
==========================================
  Files        1513     1513              
  Lines      203334   203356      +22     
  Branches     2892     2892              
==========================================
- Hits       162510   162505       -5     
- Misses      40276    40303      +27     
  Partials      548      548              

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