Fix updating the password of a link share when passwords are enforced

The password input was shown in the popup menu when passwords were not
enforced, or when they were enforced but no password was set, which
prevented updating/changing the password once set. As the popover menu
is shown only when the share is a link share, and the password input
should be shown too when password are enforced and a password is set no
condition is needed, so now the password input is always shown.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>