Minor: simplify the function GenericListArray::get_type

[HaoYang670]

Signed-off-by: remzi [email protected]

Which issue does this PR close?

None.

Rationale for this change

Just to make the code more readable.

What changes are included in this PR?

Replace if-else branches by pattern matching.

Are there any user-facing changes?

No.

[codecov-commenter]

Codecov Report

Merging #1650 (31fd858) into master (e51de5e) will decrease coverage by 0.00%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master    #1650      +/-   ##
==========================================
- Coverage   83.08%   83.08%   -0.01%     
==========================================
  Files         193      193              
  Lines       55778    55775       -3     
==========================================
- Hits        46343    46338       -5     
- Misses       9435     9437       +2     

Impacted Files	Coverage Δ
arrow/src/array/array_list.rs	95.79% <66.66%> (+0.17%)	⬆️
arrow/src/datatypes/datatype.rs	66.40% <0.00%> (-0.40%)	⬇️
parquet/src/encodings/encoding.rs	93.37% <0.00%> (-0.19%)	⬇️
arrow/src/array/transform/mod.rs	86.57% <0.00%> (-0.12%)	⬇️

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