reactivex: fix ascii issue

Co-Authored-By: Jed Fox <git@twopointzero.us>

assets/stylesheets/pages/_reactivex.scss

@@ -28,7 +28,7 @@
       margin-top: 0;
 
       &:before {
-        content: "…";
+        content: "\2026";
       }
     }