Remoe unnecessary `$` on arithmetic variables in shell script

unbound.sh

@@ -5,16 +5,16 @@ ZONES_DIR="/opt/unbound/etc/unbound/zones"
 
 reserved=12582912
 availableMemory=$((1024 * $( (fgrep MemAvailable /proc/meminfo || fgrep MemTotal /proc/meminfo) | sed 's/[^0-9]//g' ) ))
-if [ $availableMemory -le $(($reserved * 2)) ]; then
+if [ $availableMemory -le $((reserved * 2)) ]; then
     echo "Not enough memory" >&2
     exit 1
 fi
-availableMemory=$(($availableMemory - $reserved))
-msg_cache_size=$(($availableMemory / 3))
-rr_cache_size=$(($availableMemory / 3))
+availableMemory=$((availableMemory - reserved))
+msg_cache_size=$((availableMemory / 3))
+rr_cache_size=$((availableMemory / 3))
 nproc=$(nproc)
 if [ "$nproc" -gt 1 ]; then
-    threads=$(($nproc - 1))
+    threads=$((nproc - 1))
 else
     threads=1
 fi