fix(r): Ensure ordered is reflected in na_dictionary()

[paleolimbot]

Closes #296.

library(nanoarrow)

arrow::as_data_type(na_dictionary(na_string(), ordered = FALSE))
#> DictionaryType
#> dictionary<values=string, indices=int32>
arrow::as_data_type(na_dictionary(na_string(), ordered = TRUE))
#> DictionaryType
#> dictionary<values=string, indices=int32>

arrow::as_data_type(
  infer_nanoarrow_schema(factor(letters[1:5], ordered = TRUE))
)
#> DictionaryType
#> dictionary<values=string, indices=int32>
arrow::as_data_type(
  infer_nanoarrow_schema(factor(letters[1:5], ordered = FALSE))
)
#> DictionaryType
#> dictionary<values=string, indices=int32>

^{Created on 2023-09-18 with reprex v2.0.2}

[codecov-commenter]

Codecov Report

Merging #299 (1859a95) into main (804630d) will decrease coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #299      +/-   ##
==========================================
- Coverage   86.97%   86.93%   -0.04%     
==========================================
  Files          69       66       -3     
  Lines       10553    10201     -352     
==========================================
- Hits         9178     8868     -310     
+ Misses       1375     1333      -42     

Files Changed	Coverage Δ
r/R/type.R	100.00% <100.00%> (ø)

... and 3 files with indirect coverage changes

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