boost: Updates package to version 1.81.0

boost: Updates package to version 1.81.0

This commit updates boost to version 1.81.0

A new library is available:
- URL [1]: A library for parsing, modifying, and printing URLs using
only C++11, from Vinnie Falco and Alan de Freitas. Features include
fast compilation, strong invariants, and strict compliance using a
memory-friendly approach.

More info about Boost 1.81.0 can be found at the usual place [2].

[1]: https://www.boost.org/doc/libs/1_81_0/libs/url/doc/html/index.html
[2]: https://www.boost.org/users/history/version_1_81_0.html

Signed-off-by: Carlos Miguel Ferreira <carlosmf.pt@gmail.com>