Remove duplicate candidates when setting tags

* lisp/org.el (org-set-tags): Remove duplicate candidates from menu.

lisp/org.el

@@ -15025,13 +15025,14 @@ When JUST-ALIGN is non-nil, only align tags."
 		    (let* ((table
 			    (setq
 			     org-last-tags-completion-table
+			     (delete-dups
 			      (append
 			       org-tag-persistent-alist
 			       (or org-tag-alist (org-get-buffer-tags))
 			       (and
 				org-complete-tags-always-offer-all-agenda-tags
 				(org-global-tags-completion-table
-				(org-agenda-files))))))
+				 (org-agenda-files)))))))
 			   (current-tags (org-split-string current ":"))
 			   (inherited-tags
 			    (nreverse (nthcdr (length current-tags)