You can remove the first rear shock without any drama. The entire load of the rear wheel, tire, brake, and swingarm are now on that second rear shock. Place some plywood sheets or anything that is the right height under the rear tire so it is just barely on the boards. This will make removing the bolts on that second shock very easy as there will be minimal load them. This pic shows the swingarm still in the proper position even though both shocks are removed.