Make lit implementation more concise

[alamb]

Which issue does this PR close?

re #2827

Rationale for this change

@andygrove suggested the code in #2828 could be made more concise: https://github.com/apache/arrow-datafusion/pull/2828/files#r912398460

What changes are included in this PR?

make code more concise

Are there any user-facing changes?

No

[codecov-commenter]

Codecov Report

Merging #2838 (050a3e1) into master (bf7564f) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2838      +/-   ##
==========================================
- Coverage   85.19%   85.18%   -0.01%     
==========================================
  Files         275      275              
  Lines       48761    48764       +3     
==========================================
+ Hits        41541    41542       +1     
- Misses       7220     7222       +2     

Impacted Files	Coverage Δ
...atafusion/physical-expr/src/expressions/literal.rs	100.00% <100.00%> (ø)
datafusion/expr/src/logical_plan/plan.rs	74.11% <0.00%> (-0.20%)	⬇️
datafusion/common/src/scalar.rs	75.66% <0.00%> (-0.12%)	⬇️

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[andygrove]

Thanks @alamb