Fix language selector alignment

Depending on the screen, it could appear a bit to the left of where it
was supposed to be.

app/assets/stylesheets/layout.scss

@@ -636,7 +636,10 @@ body > header,
 .top-links {
   background: $dark;
   font-size: $small-font-size;
-  padding-right: $line-height / 2;
+
+  > :first-child {
+    @include grid-column-gutter;
+  }
 
   a {
     color: inherit;

app/assets/stylesheets/layout/locale_switcher.scss

@@ -2,7 +2,6 @@
   @include has-fa-icon(angle-down, solid, after);
   float: left;
   margin-bottom: $line-height / 4;
-  margin-left: $line-height / 2;
   margin-top: $line-height / 4;
   position: relative;