MicMute broke in recent Zoom update

In Zoom version 5.17.5 MicMute broke because the menu bar items have been slightly altered.

This is fixed by changing
```
zoom:selectMenuItem'Mute Audio' -> zoom:selectMenuItem'Mute audio' 
zoom:selectMenuItem'Unmute Audio' -> zoom:selectMenuItem'Unmute audio' 
```

in `MicMute.spoon/init.lua`

Since `selectMenuItem` supports regex, I'd suggest a solution that works for both cases.