Cannot set custom HTML attributes for the min and step attributes

[ipokkel]

Describe the bug
When setting html_attributes options for min and step these attribute values are not set for the element as per field creation code.

To Reproduce
Steps to reproduce the behavior:

1. Create a code snippet for the site that creates a number field and add min and step to the html_attributes option.

$fields[] = new PMProRH_Field(
	'test_number_min_step', // input field name, used as meta key
	'number',         // field type
	array(
		'label'           => 'Number Test', // display custom label, if not used field name will be used
		'html_attributes' => array(
			'min'  => '5',
			'step' => '5',
		), // add valid html input field attributes
		'hint'            => 'This is a test of html attributes for a number field', // display a hint under field
		'profile'         => true, // show on profile
	)
);

2. Navigate to the Membership Checkout page on the frontend.
3. Inspect rendered HTML for the number field.
4. See error

<input type="number" min="0" step="1" pattern="\d+" id="test_number_min_step" name="test_number_min_step" value="" size="5" class="input ">

Expected behavior
That HTML attributes created for a field to be set in the rendered HTML for the element

Isolating the problem (mark completed items with an [x]):

• I have deactivated other plugins and confirmed this bug occurs when only Paid Memberships Pro plugin is active.
• This bug happens with a default WordPress theme active, or Memberlite.
• I can reproduce this bug consistently using the steps above.