falsisign.sh: make rotation selection less cumbersome

falsisign.sh

@@ -133,7 +133,7 @@ do
     else
         if [ -z "${FIXED_ROTATION+x}" ]
         then
-            ROTATION=$(shuf -n 1 -e '-' '')$(shuf -n 1 -e $(seq 0 .1 2))
+            ROTATION=$(seq -2 .1 2 | shuf -n 1)
         else
             ROTATION="${FIXED_ROTATION}"
         fi