package/fetchmail: bump version to 6.4.29

Updated license hash due to OpenBSD-related upstream commit:
https://sourceforge.net/p/fetchmail/git/ci/c4419bdd2557321b268f6e105d511923b9a35936/



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>