Remove out of date comment

[alamb]

re #996

@jhorstmann points out that bool no longer implements ArrowNativeType and thus this comment it out of date. Remove it

Here are the types that implement ArrowNativeType

/Users/alamb/Software/arrow-rs/arrow/src/datatypes/native.rs
118: impl ArrowNativeType for i8 {
141: impl ArrowNativeType for i16 {
164: impl ArrowNativeType for i32 {
193: impl ArrowNativeType for i64 {
222: impl ArrowNativeType for u8 {
245: impl ArrowNativeType for u16 {
268: impl ArrowNativeType for u32 {
291: impl ArrowNativeType for u64 {
326: impl ArrowNativeType for f16 {}
327: impl ArrowNativeType for f32 {}
328: impl ArrowNativeType for f64 {}

[codecov-commenter]

Codecov Report

Merging #1008 (9e6cabd) into master (5806d29) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1008   +/-   ##
=======================================
  Coverage   82.31%   82.31%           
=======================================
  Files         168      168           
  Lines       49031    49031           
=======================================
  Hits        40360    40360           
  Misses       8671     8671           

Impacted Files	Coverage Δ
arrow/src/buffer/immutable.rs	97.84% <ø> (ø)
arrow/src/datatypes/field.rs	53.37% <0.00%> (-0.31%)	⬇️
parquet_derive/src/parquet_field.rs	66.21% <0.00%> (+0.22%)	⬆️

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