Bump the requirement to v3.6.3, which means we can remove the final
ifdef guard and all the builds have TLS 1.3 support.
It was released over 7 years ago, with 2 new feature releases since
then and dozen of bugfix releases in the 3.6 branch.
The oldest distributions we target Ubuntu 20.04 and Debian Bullseye,
have 3.6.13 and 3.7.1 respectively.
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Emil Velikov
87eb6cc7e1