It's possible that the cable for your brakes came as a unit (wire, housing, pinch bolt, barrel adjuster) and doesn't come apart, as did the brake cables on my 1954 3-speed (there's a picture link in my 3-speed thread that shows both ends of that cable). The SA catalog picture shows a barrel adjuster on the housing end. Your bike doesn't have that. Is that an adjuster on the pinch-bolt end? If there is an adjuster, I'd say to screw it in all the way and then see if there is enough slack to remove the cable from the u-bolts. But in your case, if that is an adjuster, looks like it's already bottomed out. Another way to get cable slack would be to pull the cable off the brake lever. There should be a ferrule between the housing and lever that you can pull back and then slip the wire through the groove. The anchor end should also pull out through a groove.