"Sculpt vertex colors" from f7bbc7cdbb6cb0d2850 are now replaced
with generic color attributes. The operators and functions for adding
and removing those layers still existed though.
This does break RNA compatibility, but the RNA API always referred
to the features which were behind an experimental flag, so there shouldn't
be code depending on it. The attribute API is a direct replacement anyway.
Removing these operators and RNA properties also prevents people
from depending on them only to have them removed.