[3.6] bpo-31849: Fix warning in pyhash.c (GH-6799)

[miss-islington]

(cherry picked from commit a8eb585)

Co-authored-by: A. Jesse Jiryu Davis [email protected]

https://bugs.python.org/issue31849

[miss-islington]

@ajdavis and @methane: Backport status check is done, and it's a success ✅ .

[miss-islington]

@ajdavis and @methane: Backport status check is done, and it's a success ✅ .

[Mariatta]

I'm investigating why miss-islington did not merge the PR even though it's been approved.

[Mariatta]

The PR was not automerged because at that time, appveyor was a required status check, but it did not run.
Appveyor status check has been disabled now, so I'll get miss-islington to merge this.

[miss-islington]

@ajdavis and @methane: Backport status check is done, and it's a success ✅ .

[miss-islington]

Thanks!