In the MP3 Export dialog "Extreme" would be more appropriate as "Excellent"

### Your idea

For 3.7.0 in the MP3 export dialog in the Quality dropdown menu we have replaced the word **Insane** with **Excessive**, see #7008

I suggest that we also change the word **Extreme** to **Excellent** as more appropriate terminolgy.

This range is 220 to 260 kbps - and 256 kbps is regarded as a pretty 'normal' setting to use for MP3s now that disks are so much larger and cheaper. _It's certainly what I used once I upgraded from my original small disk iPod to a 160GB iPod Classic_

### Problem to be solved

Using **Extreme** acts as a discouragement to users to use this setting

### Prior art

Audacity 3.7.0 alpha


### Additional context

See #7008