hadrian: Fix typo in docs/users_guide
Reported by @alanz (#17352 (closed)). This passed validation because the hadrian
build apparently runs with --docs=no-sphinx
since 9aa27273 (although it's not clear why this was done)
Reported by @alanz (#17352 (closed)). This passed validation because the hadrian
build apparently runs with --docs=no-sphinx
since 9aa27273 (although it's not clear why this was done)