The code had this as 26.03, but the documentation said 26.06. The
usual deprecation period is a year, so I'm changing the documentation.
Unfortunately the documentation (fe4d5036c2) was updated separately
from the code (afb54ff8e8), so this wasn't obvious at the time!
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
3af6fd2f30