[C++] Fix typos and spelling

[asfimport]

Fix typo under cpp directory

Reporter: Kazuaki Ishizaki / @kiszk
Assignee: Kazuaki Ishizaki / @kiszk

PRs and other links:

• GitHub Pull Request #8520

_{Note: This issue was originally created as ARROW-10384. Please see the migration documentation for further details.}

[asfimport]

Kouhei Sutou / @kou:
Issue resolved by pull request 8520
#8520