remove unnecessary code

docker/frontend/entrypoint.sh

@@ -7,7 +7,7 @@ BACKEND_DIR="$APP_DIR/apps/backend"
 PUBLIC_DIR="$BACKEND_DIR/public"
 PHP_PORT=9000
 
-/usr/local/bin/wait-for-it.sh "BACKEND_DIR:$PHP_PORT" -t 300
+/usr/local/bin/wait-for-it.sh "$BACKEND_DIR:$PHP_PORT" -t 300
 
 cd "$FRONTEND_DIR"
 npm ci --prefer-offline --no-audit