Use number field type for number fields

[laryn]

It looks like this was in place at one point and removed until browser support warranted it:

• webform/components/number.inc

  Lines 246 to 255 in 6b4a02f

  	// This IF statement is mostly in place to allow our tests to set type="text"
  	// because SimpleTest does not support type="number".
  	if (!isset($element['#attributes']['type'])) {
  	// HTML5 number fields are no long used pending better browser support.
  	// See issues #2290029, #2202905.
  	// @code
  	// $element['#attributes']['type'] = 'number';
  	// @endcode
  	$element['#attributes']['type'] = 'text';
  	}

I'm not sure if it's as simple as uncommenting the line above.

Earlier related Drupal issue that led to reverting to text field:

• https://www.drupal.org/project/webform/issues/2290029