In the plugin gravityformsuserregistration the default password field is built on GF_Field_Text(), to enable the visibility of the password it should be changed to GF_Field_Password().
Here is the code that is needed (class-gf-user-registration.php line 2418), would be nice if its updated in the next release.
/* Create password field. */
$password_field = new GF_Field_Password();
$password_field->id = 2;
$password_field->formId = 0;
$password_field->isRequired = true;
//$password_field->enablePasswordInput = true;
$password_field->passwordVisibilityEnabled = true;
//$password_field->isHidden = true;
$password_field->label = esc_html__( 'Password', 'gravityformsuserregistration' );
$password_field->inputs = array(
array(
'id' => '2',
'label' => esc_html__( 'enter Password', 'gravityformsuserregistration' ),
'customLabel' => esc_html__( 'Password', 'gravityformsuserregistration' ),
'placeholder' => esc_html__( 'Please enter your password', 'gravityformsuserregistration' )
),
array(
'id' => '2.2',
'isHidden' => true
),
);