package/libmicrohttpd: bump version to 0.9.75
Release notes:
https://lists.gnu.org/archive/html/libmicrohttpd/2021-12/msg00052.html
https://lists.gnu.org/archive/html/libmicrohttpd/2021-12/msg00056.html
Changelog:
https://git.gnunet.org/libmicrohttpd.git/tree/ChangeLog
Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>