win build: revert pyinstaller upgrade
win build: revert pyinstaller upgrade

Various issues with newer versions... needs more investigation.

This reverts part of https://github.com/spesmilo/electrum/commit/2b4bf19c0629971a5989d338daa600e2d11241a8

spesmilo/electrum,spesmilo/electrum,wakiyamap/electrum-mona,pooler/electrum-ltc,wakiyamap/electrum-mona,pooler/electrum-ltc,wakiyamap/electrum-mona,pooler/electrum-ltc,wakiyamap/electrum-mona,pooler/electrum-ltc,spesmilo/electrum,spesmilo/electrum