Fix in display of Float16Array

[helgikrs]

Which issue does this PR close?

Closes #1193 .

What changes are included in this PR?

Due to a typo the float16 array was being cast to a float32 array,
causing a crash when pretty printing a record batch containing float16.
Fixed that typo and added a test.

Are there any user-facing changes?

No.

[codecov-commenter]

Codecov Report

Merging #1194 (d53b3e0) into master (713bd6d) will not change coverage.
The diff coverage is 0.00%.

❗ Current head d53b3e0 differs from pull request most recent head e0c4172. Consider uploading reports for the commit e0c4172 to get more accurate results

@@           Coverage Diff           @@
##           master    #1194   +/-   ##
=======================================
  Coverage   82.70%   82.70%           
=======================================
  Files         173      173           
  Lines       51055    51055           
=======================================
  Hits        42225    42225           
  Misses       8830     8830           

Impacted Files	Coverage Δ
arrow/src/util/display.rs	19.62% <0.00%> (ø)
parquet_derive/src/parquet_field.rs	65.75% <0.00%> (-0.23%)	⬇️
arrow/src/array/transform/mod.rs	85.43% <0.00%> (-0.14%)	⬇️
parquet/src/encodings/encoding.rs	93.71% <0.00%> (+0.19%)	⬆️
arrow/src/datatypes/field.rs	54.10% <0.00%> (+0.30%)	⬆️

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[alamb]

Thanks @helgikrs