Fix tabbing beyond last row of raw tag editor in Firefox

(closes #5847)

- removed the stopPropagation from the combobox keydown handler
  to make sure that the raw_tag_editor keydown handler will run

- increased timeout from 1ms to 10ms for Firefox
  This is related to Firefox's newish time budgeting approach that they
  started using around Firefox 55.  As a result, very fast timers (<4ms?)
  may run synchronously instead of yielding and running asynchronously
  https://blog.wanderview.com/blog/2017/03/13/firefox-52-settimeout-changes/

  (note similar code in ui/fields/combo.js to delay focus changes and
  redraws 10ms after the tag changes and other events have completed)

modules/ui/combobox.js

@@ -177,7 +177,6 @@ export function uiCombobox(context, klass) {
                     break;
 
                 case 9:   // ⇥ Tab
-                    d3_event.stopPropagation();
                     accept();
                     break;
 

modules/ui/raw_tag_editor.js

@@ -366,7 +366,7 @@ export function uiRawTagEditor(context) {
                 _showBlank = true;
                 content(wrap);
                 list.selectAll('li:last-child input.key').node().focus();
-            }, 1);
+            }, 10);
         }
     }