[electrum] pinpoint packaging lib and specify hashes for MacOS build

Summary:
Bumping pyinstaller-hooks-contrib in D16719 introduced another indirect dependency for the build process on MacOS.

This change should have been included in that commit but was accidentaly stashed while testing.

Test Plan:
contrib/osx/make_osx

Check for no errors

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D16725