Re: convert-ly warnings too global

[Werner LEMBERG]

>> If I do
>> 
>> ```
>> convert-ly en/notation/rhythms.itely > /dev/null
>> ```
>> 
>> I get the following two warnings.
>> 
>> 
>> ```
>> Not smart enough to convert music following \fine.
>> 
>> Warning: \fine no longer enforces the end of the music.  If your piece
>> has music following \fine that you want to exclude when it is
>> unfolded, use \volta to exclude it.
>> Please refer to the manual for details, and update manually.
>> 
>> Not smart enough to convert BreathingSign to Divisio.
>> 
>> MensuralStaff and VaticanaStaff now use Divisio_engraver to engrave
>> divisiones as Divisio grobs.
>> 
>> Previously, the respective Voice-aliased contexts used
>> Breathing_sign_engraver to engrave divisiones as BreathingSign grobs.
>> Because of the new names and the move from Voice to Staff, layout
>> adjustments for the old scheme are not effective for the new.
>> 
>> If you are not content with the new default layout, deal with Divisio
>> and Divisio_engraver in the appropriate Staff-aliased context.
>> Please refer to the manual for details, and update manually.
>> ```
>> 
>> 
>> AFAICS, these warnings are unfounded; they are rather artifacts of
>> `convert-ly`, which applies regular expressions 'too globally'.

This was a thinko on my side: `convert-ly` uses the line

```
@c \version "2.21.0"
```

at the very beginning of `en/notation/rhythms.itely`; it is fully
sufficient to 'lift' this version number to something higher than the
warning.

Sorry for the noise.


    Werner