incorrect version number in convert-ly rule

[Graham Percival]

The vertical space renaming uses
  @rule ((2, 13, 36))
but that should be 39.  Unfortunately, simply updating this value
in python/convert-ly might cause problems when previously-updated
files (now incorrectly tagged as .36) try to be updated to .39
again.

I'm willing to handle all the manual version updating if nobody
else wants to do it.

- Graham