mu: better handle updating mail being viewed

instead of the the 'noupdate', add 'noview', so the headers still get
update but we don't render unread mail twice.

mu4e/mu4e-view.el

@@ -903,7 +903,7 @@ changes, it triggers a refresh."
 	;; mark /all/ messages with this message-id as read, so all copies of
 	;; this message will be marked as read. We don't want an update thougn,
 	;; we want a full message, so images etc. work correctly.
-	(mu4e~proc-move msgid nil "+S-u-N" 'noupdate)
+	(mu4e~proc-move msgid nil "+S-u-N" 'noview)
         (mu4e~proc-view docid mu4e-view-show-images (mu4e~decrypt-p msg))
 	t))))