Address feature highlight popover inconsistencies

app/assets/stylesheets/components/popover.scss

@@ -87,7 +87,7 @@
 }
 
 .popover-body {
-  padding: $gl-padding;
+  padding: $gl-padding $gl-padding-12;
 
   > .popover-hr {
     margin: $gl-padding 0;

app/assets/stylesheets/framework/feature_highlight.scss

@@ -39,7 +39,7 @@
   display: none;
 
   hr {
-    margin: $gl-padding * 0.5 0;
+    margin: $gl-padding 0;
   }
 
   .btn-link {
@@ -71,9 +71,6 @@
 
 .feature-highlight-popover {
   width: 240px;
-  padding: 0;
-  border: 1px solid $border-color;
-  box-shadow: 0 2px 4px $dropdown-shadow-color;
 
   &.right > .arrow {
     border-right-color: $border-color;
@@ -85,7 +82,7 @@
 }
 
 .feature-highlight-popover-sub-content {
-  padding: 9px 14px;
+  padding: $gl-padding $gl-padding-12;
 }
 
 @include keyframes(pulse-highlight) {

app/assets/stylesheets/framework/variables.scss

@@ -336,6 +336,7 @@ $tooltip-font-size: 12px;
  */
 $gl-padding-4: 4px;
 $gl-padding-8: 8px;
+$gl-padding-12: 12px;
 $gl-padding: 16px;
 $gl-padding-24: 24px;
 $gl-padding-32: 32px;