fix(slider): no label is rendered when the labelText property is not specified.

src/Slider/Slider.svelte

@@ -139,6 +139,7 @@
   on:mouseenter
   on:mouseleave
 >
+  {#if labelText || $$slots.labelText}
     <label
       for="{id}"
       id="{labelId}"
@@ -149,6 +150,7 @@
         {labelText}
       </slot>
     </label>
+  {/if}
   <div
     class:bx--slider-container="{true}"
     style="{fullWidth ? 'width: 100%' : undefined}"