Remove needless quote

Before: broken command line option
  curl -qsILf "" "$1" >&4 2>&1
  curl -qsILf "--ipv4" "$1" >&4 2>&1

After:
  curl -qsILf "$1" >&4 2>&1
  curl -qsILf --ipv4 "$1" >&4 2>&1