fix some typos in code and comments

[jimexist]

Which issue does this PR close?

Closes #.

Rationale for this change

fix typos in code and comment, because cleaner code and typo free code is more search friendly

What changes are included in this PR?

Are there any user-facing changes?

[codecov-commenter]

Codecov Report

Merging #985 (f96c5b0) into master (f6908bf) will not change coverage.
The diff coverage is 66.66%.

@@           Coverage Diff           @@
##           master     #985   +/-   ##
=======================================
  Coverage   82.31%   82.31%           
=======================================
  Files         168      168           
  Lines       48761    48761           
=======================================
  Hits        40136    40136           
  Misses       8625     8625           

Impacted Files	Coverage Δ
arrow/src/buffer/immutable.rs	97.84% <ø> (ø)
arrow/src/buffer/mutable.rs	89.47% <ø> (ø)
arrow/src/bytes.rs	56.25% <ø> (ø)
arrow/src/compute/kernels/arity.rs	86.36% <ø> (ø)
arrow/src/compute/kernels/cast_utils.rs	87.50% <ø> (ø)
arrow/src/csv/reader.rs	90.58% <ø> (ø)
arrow/src/datatypes/schema.rs	66.93% <ø> (ø)
arrow/src/compute/kernels/filter.rs	89.55% <33.33%> (ø)
arrow/src/compute/kernels/cast.rs	94.81% <100.00%> (ø)
arrow/src/datatypes/field.rs	53.37% <0.00%> (-0.31%)	⬇️
... and 1 more

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[alamb]

Nice @jimexist -- keeping things neat and tidy 🧹 thank you