Move CSS of hover underline to base from color variants

scss/_badge.scss

@@ -14,6 +14,12 @@
   vertical-align: baseline;
   @include border-radius($badge-border-radius);
 
+  &[href] {
+    @include hover-focus {
+      text-decoration: none;
+    }
+  }
+
   // Empty badges collapse automatically
   &:empty {
     display: none;

scss/mixins/_badge.scss

@@ -5,7 +5,6 @@
   &[href] {
     @include hover-focus {
       color: color-yiq($bg);
-      text-decoration: none;
       background-color: darken($bg, 10%);
     }
   }