heads up - default erlang version will change to OTP26

hi

every year the OTP team bumps their supported erlang versions, and its time we
do the same.

I'll do this in the next 2 weeks so that they land in the 2025Q1 branch when its
forked early next year.

Aside from databases/leofs (still using OTP21!) all the other ports now build
their own releases, and don't have a direct lang/erlang dependency at runtime.

Also as Elixir 1.18.0 has been released, lang/elixir will move to 1.17.3 as well.

Happy BEAMing
Dave