Prevent Recaptcha from keeping focus when popup dismissed.

Best solution for now since we still have to support the outgoing
version.  When the outgoing version is gone, we may be able to
remove the strict anti-scroll measures, and this will no longer
be necessary.

src/Posting/Captcha.v2.coffee

@@ -237,6 +237,9 @@ Captcha.v2 =
         if $ 'iframe[src^="https://www.google.com/recaptcha/api2/frame"]', node
           new MutationObserver(@fixBubble.bind(@, node)).observe node,
             attributes: true
+          # Prevent Recaptcha from keeping focus when popup dismissed.
+          if overlay = $ 'div[style*="position: fixed;"]', node
+            $.on overlay, 'click', -> $('#qr iframe')?.blur()
 
   fixBubble: (node) ->
     {bottom, right, width} = node.getBoundingClientRect()