Update qutebrowser.org/doc/faq.html question

'What's the difference between insert and passthrough mode?'
to reflect escape->shift+escape keybinding change

Author: nat-west

doc/faq.asciidoc

@@ -211,9 +211,10 @@ Why does J move to the next (right) tab, and K to the previous (left) one?::
 
 What's the difference between insert and passthrough mode?::
     They are quite similar, but insert mode has some bindings (like `Ctrl-e` to
-    open an editor) while passthrough mode only has escape bound. It might also
-    be useful to rebind escape to something else in passthrough mode only, to be
-    able to send an escape keypress to the website.
+    open an editor) while passthrough mode only has shift+escape bound. This is
+    because shift+escape is unlikely to be a useful binding to be passed to a
+    webpage. However, any other keys may be assigned to leaving passthrough mode
+    instead of shift+escape should this be desired.
 
 Why does it take longer to open a URL in qutebrowser than in chromium?::
     When opening a URL in an existing instance, the normal qutebrowser