Remove the vendor name from the "is playing media" notification on Linux

E.g., the media is playing notification is called "Mullvad Mullvad Browser Nightly" on Linux.

Probably the problem is with upstream strings (IIRC, there's a string that would be "Mozilla Firefox", without concatenating "Mozilla" and "Firefox", which is our problem here). In case, we should find them and ask them to be changed upstream.

For Tor Browser, it says "Tor Project Tor Browser", which isn't ideal either.