[Python] Add support for Python 3.9 macOS wheels

[asfimport]

Reporter: Terence Honles / @terencehonles
Assignee: Terence Honles / @terencehonles

Related issues:

• Can't install pyarrow with python 3.9.1 (duplicates)
• [Python] Add support for Python 3.9 except macOS wheel and Windows wheel (is related to)

PRs and other links:

• GitHub Pull Request #8915

_{Note: This issue was originally created as ARROW-10904. Please see the migration documentation for further details.}

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Terence Honles / @terencehonles:
Broken out of ARROW-10224. MacOS wheels were passing at one point, but the builder will likely need to be rewritten off of TravisCI.

[asfimport]

Kouhei Sutou / @kou:
Issue resolved by pull request 8915
#8915