[FIX] mail: fix push to talk key detection

Before this commit, the push to talk key combination was wrongly
detected. Indeed, it was dependent on which key was pressed first.

Steps to reproduce:
- Register "ctrl + alt" as the push to talk key
- Press control then alt, push to talk does not work
- Press alt then control, push to talk works
- If you unpress the alt key, the push to talk will stop as expected
- If you unpress the control key, the push to talk will keep going

This commit fixes the issue.

closes odoo/odoo#134639

Signed-off-by: Thanh Son Dodeur (tso) <tso@odoo.com>