Slider Examples with aria-orientation and aria-valuetext: Fix CSS bug…

… so labels have consistent appearance (pull #1593)

The Temperature label for the vertical slider in Slider Examples with aria-orientation and aria-valuetext is bold, but the labels for the text sliders (Fan and Heat/Cool) were not.
This commit adds a missing period to the css selector so all the labels are bold.

Co-authored-by: Matt King <a11yThinker@Gmail.com>

examples/slider/css/text-slider.css

@@ -40,7 +40,7 @@ div.aria-widget-text-slider div.value {
   position: absolute;
 }
 
-div.aria-widget-text-slider label {
+div.aria-widget-text-slider .label {
   display: block;
   margin-top: 0.5em;
   margin-bottom: 0.5em;