Fix misalignment of navigation bar with post body

There was a regression in the template updates where the navigation bar no longer aligns with the post left margin at normal viewport.

_sass/_masthead.scss

@@ -52,7 +52,7 @@
   white-space: nowrap;
 
   &--lg {
-    padding-right: 3em;
+    padding-right: 2em;
     font-weight: 700;
   }
 }