fix bash syntax error in common.sh

scripts/common.sh

@@ -40,7 +40,7 @@ function dch_custom() {
 
 function dch_backport() {
 	local version, name
-	version=$(cat /etc/os-release | grep VERSION_ID= | sed -E 's/.*([0-9]+).*/\1/'))
+	version=$(cat /etc/os-release | grep VERSION_ID= | sed -E 's/.*([0-9]+).*/\1/')
 	name=$(cat /etc/os-release | grep VERSION= | sed 's/.*(\(.*\)).*/\1/')
 	debchange --local ~bpo$version+ --distribution $name-backports "Rebuild for $name-backports."
 }