remove redundant session token

src/scripts/backupapp.sh

@@ -13,7 +13,7 @@ if [[ $# == 1 && "$1" == "--check" ]]; then
 fi
 
 if [ $# -lt 4 ]; then
-    echo "Usage: backupapp.sh <appid> <url> <url> <key> [aws session token]"
+    echo "Usage: backupapp.sh <appid> <url> <url> <key>"
     exit 1
 fi
 
@@ -23,7 +23,6 @@ app_id="$1"
 backup_url="$2"
 backup_config_url="$3"
 backup_key="$4"
-session_token="$5" # unused since it seems to be part of the url query param in v4 signature
 readonly now=$(date "+%Y-%m-%dT%H:%M:%S")
 readonly app_data_dir="${DATA_DIR}/${app_id}"
 readonly app_data_snapshot="${DATA_DIR}/snapshots/${app_id}-${now}"