fix(tabs): fix scss compile error on some versions of sass Closes #2719

Author: perrygovier

scss/_tabs.scss

@@ -124,7 +124,7 @@
 }
 
 @mixin tabs-background($style, $color, $border-color) {
-  &.#{$style} {
+  .#{$style} {
     .tabs,
     &> .tabs{
       background-color: $color;
@@ -143,7 +143,7 @@
 }
 
 @mixin tabs-color($style, $color) {
-  &.#{$style} {
+  .#{$style} {
     .tab-item {
       color: rgba($color, $tabs-off-opacity);
       opacity: 1;