Fixes #2024, simplifies padding logic for selection item

src/definitions/modules/dropdown.less

@@ -400,7 +400,7 @@ select.ui.dropdown {
 /* Scrollbar in IE */
 @media all and (-ms-high-contrast:none) {
   .ui.selection.dropdown .menu {
-    min-width: ~"calc(100% - "@scrollBarWidth~")";
+    min-width: ~"calc(100% - "@scrollbarWidth~")";
   }
 }
 
@@ -428,9 +428,7 @@ select.ui.dropdown {
 /* Menu Item */
 .ui.selection.dropdown .menu > .item {
   border-top: @selectionItemDivider;
-  padding-left: @selectionHorizontalPadding !important;
-  /* Add in spacing for scroll bar */
-  padding-right: ~"calc("@selectionHorizontalPadding~" + 1em) !important~";
+  padding: @selectionItemPadding !important;
   white-space: normal;
   word-wrap: normal;
 }

src/themes/default/globals/site.variables

@@ -375,7 +375,7 @@
 --------------------*/
 
 /* Rendered Scrollbar Width */
-@scrollBarWidth: 15px;
+@scrollbarWidth: 15px;
 
 /* Used to match floats with text */
 @lineHeightOffset       : ((@lineHeight - 1em) / 2);

src/themes/default/modules/dropdown.variables

@@ -143,6 +143,10 @@
 @selectionMenuBoxShadow: 0px 2px 4px 0px rgba(0, 0, 0, 0.08);
 @selectionMenuItemBoxShadow: none;
 
+@selectionItemHorizontalPadding: @itemHorizontalPadding;
+@selectionItemVerticalPadding: @itemVerticalPadding;
+@selectionItemPadding: @selectionItemVerticalPadding @selectionItemHorizontalPadding;
+
 @selectionTransition:
   @transition,
   box-shadow 0.2s @defaultEasing,