Update hide labels from issue board cards

This commit fixes comments given on a merge request

app/assets/stylesheets/pages/boards.scss

@@ -553,11 +553,6 @@
    */
   height: 34px;
 
-  label {
-    font-weight: $gl-font-weight-normal;
-    margin-bottom: 0;
-  }
-
   @include media-breakpoint-down(sm) {
     margin-bottom: 10px;
   }

ee/app/assets/javascripts/boards/toggle_labels.js

@@ -42,7 +42,7 @@ export default () =>
         </span>
         <gl-toggle
           :value="isShowingLabels"
-          class="prepend-left-10"
+          class="prepend-left-10 mb-0"
           :label-on="toggleOnLabel"
           :label-off="toggleOffLabel"
           aria-describedby="board-labels-toggle-text"