mu4e: use mu4e-view-rendered-hook

Instead of the older mu4e-after-view-message-hook; update version where
it go obsolete.

mu4e/mu4e-view.el

@@ -637,7 +637,7 @@ As a side-effect, a message that is being viewed loses its
         (mu4e-error "Cannot get a message view"))
       (select-window mu4e~headers-view-win)))
   (with-current-buffer gnus-article-buffer
-    (run-hooks 'mu4e-after-view-message-hook)))
+    (run-hooks 'mu4e-view-rendered-hook)))
 
 (defun mu4e-view-message-text (msg)
   "Return the pristine MSG as a string."