Remove json_object typedef
The json-c header already defines the same typedef. While C11 allows typedef redefinition to the same type, older versions of gcc disallow that.
In file included from lib/luks2/luks2_internal.h:32, from lib/luks2/luks2_disk_metadata.c:24: lib/luks2/luks2.h:86: error: redefinition of typedef 'json_object'
Signed-off-by: Baruch Siach baruch@tkos.co.il