arrow

GH-45027: [C++] Include path in the documentation is wrong (#45031)

In the comments the includes of `(arrow/)parquet/arrow/reader.h` were broken. Removing the prefix `arrow` makes this include in line with the includes used at the top of the file.
* GitHub Issue: #45027

Authored-by: Nis Meinert <nis.meinert@gmail.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>