helpers/generate_common.sh: update usign version to be used

Upstream fixed problem with invalid hash and that way broke validation
for some of the files. Updating to latest version of usign fixes this.

helpers/generate_common.sh

@@ -13,7 +13,7 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
-USIGN_VERSION=ef6419142a3b0fbcddcccf536e3c1880302c6f89
+USIGN_VERSION=f34a383eeed6282fa16fb021157a60c75f33fdcd
 UPDATER_VERSION=master
 
 SRC_USIGN="https://git.openwrt.org/project/usign.git"