doc: update License section to switch to LGPL 2.1+
doc: update License section to switch to LGPL 2.1+

Signed-off-by: Sven Verdoolaege <e5350bbed4977f5eb8ae1dc6abd9ae59d21ace75@kotnet.org>

Ced/piplib,Ced/piplib,periscop/piplib,periscop/piplib,periscop/piplib,Ced/piplib