More Sass quality fixes

common/lib/xmodule/xmodule/css/sequence/display.scss

@@ -9,6 +9,7 @@ $seq-nav-height: 44px;
 // repeated extends - needed since LMS styling was referenced
 .block-link {
   @include border-left(1px solid $seq-nav-border-color);
+
   display: block;
 
   &:hover, &:focus {
@@ -18,6 +19,7 @@ $seq-nav-height: 44px;
 
 .topbar {
   @include clearfix();
+
   border-bottom: 1px solid $seq-nav-border-color;
 
   @media print {
@@ -27,6 +29,7 @@ $seq-nav-height: 44px;
   a {
     &.block-link {
       @include border-left(1px solid $seq-nav-border-color);
+
       display: block;
 
       &:hover, &:focus {
@@ -43,7 +46,6 @@ $seq-nav-height: 44px;
   background-repeat: no-repeat;
   border: none;
   border-radius: 0;
-
   background-clip: border-box;
   box-shadow: none;
   box-sizing: content-box;
@@ -57,6 +59,7 @@ $seq-nav-height: 44px;
 
 .sequence-nav {
   @extend .topbar;
+
   margin: 0 0 $baseline 0;
   position: relative;
   border-bottom: none;
@@ -74,6 +77,7 @@ $seq-nav-height: 44px;
 
   .sequence-list-wrapper {
     @extend %ui-depth2;
+
     position: relative;
     height: 100%;
     flex-grow: 1;
@@ -151,7 +155,9 @@ $seq-nav-height: 44px;
 
         .sequence-tooltip {
           @include text-align(left);
+
           @extend %ui-depth2;
+
           margin-top: ($baseline/5);
           background: $seq-nav-tooltip-color;
           color: $white;
@@ -176,6 +182,7 @@ $seq-nav-height: 44px;
           &::after {
             @include transform(rotate(45deg));
             @include right(18px);
+
             background: $seq-nav-tooltip-color;
             content: " ";
             display: block;
@@ -197,6 +204,7 @@ $seq-nav-height: 44px;
 
 .sequence-nav-button {
   @extend %ui-depth3;
+
   display: block;
   top: 0;
   height: 100%;