The WooCommerce account registration form provides users with a “hint” explaining how long the password should be and what characters it should include.

​The WC Password Strength Settings plugin seems to have a feature for removing / changing the password hint.

Alternatively, it looks like it should be possible to change the hint using the password_hint filter, like so (I haven’t tested this):

add_filter('password_hint', 'change_password_hint');
function change_password_hint($hint) {
  return "My new password hint";

It’s also be possible to hide the hint using CSS, like so:

.woocommerce-password-hint { display: none; }