fix msteams installer

Following:

https://answers.microsoft.com/en-us/msteams/forum/all/unable-to-install-the-new-teams-msix-silently/9e64bf40-3436-4c1f-8215-b58a926f444e

seems to work better than the previous command, which I'm sure I'd have
tested but didn't lead to Teams being available on pyrrole.