parquet/low-level-api/reader-writer.cc has some typos.

[asfimport]

There are two typos:

1. In comment: *memory consumption. -> * memory consumption.
2. reader_writer.h and reader-writer.cc are not compatible, when you use vim to edit them, it's confuse why :A doesn't work.

Reporter: Charles

PRs and other links:

• GitHub Pull Request #9870

_{Note: This issue was originally created as ARROW-12176. Please see the migration documentation for further details.}

[asfimport]

yibocai#1:
Issue resolved by pull request 9870
#9870