scripts/run_archiso.sh: fix unnecessary $/

scripts/run_archiso.sh

@@ -96,7 +96,7 @@ run_image() {
 
     qemu-system-x86_64 \
         -boot order=d,menu=on,reboot-timeout=5000 \
-        -m "size=$memory,slots=0,maxmem=$(($memory*1024*1024))" \
+        -m "size=$memory,slots=0,maxmem=$((memory*1024*1024))" \
         -smp "$cores"  \
         -k en-us \
         -name archiso,process=archiso_0 \