This property was never encouraged. The manual even stated that "You
should avoid using it, unless you absolutely have to." Since we now have
user-data which is superior in every single way and replaces this,
delete this property. The manual also has threatened people for years
with the line "It's a makeshift solution which could go away any time
(for example, when a better solution becomes available)." We were nice
and deprecated it in 1d00aee8e1 for a
while to give script authors some time to update. Let's remove it for
good now.
86b498ecc0