Use currently opened view of Gnus article buffer

When `ace-link-gnus' is called from the summary buffer, use
the currently opened article buffer instead of switching to
the selected article (which might be different).
Also, do not jump to the next button, as this might lead to
unintended scrolling of the article buffer.

ace-link.el

@@ -417,7 +417,11 @@ If EXTERNAL is double prefix, browse in new buffer."
   (interactive)
   (save-selected-window
     (when (eq major-mode 'gnus-summary-mode)
-      (gnus-summary-widget-forward 1))
+      (if-let ((win (gnus-get-buffer-window gnus-article-buffer 'visible)))
+          (progn
+            (select-window win)
+            (select-frame-set-input-focus (window-frame win)))
+        (user-error "No article window found")))
     (let ((pt (avy-with ace-link-gnus
                 (avy-process
                  (ace-link--gnus-collect)