Prevent superfluous colon

* org.el (org-make-link-string): Prevent superfluous colon.

lisp/org.el

@@ -8450,7 +8450,7 @@ according to FMT (default from `org-email-link-description-format')."
 	     (not (equal link (org-link-escape link))))
     (setq description (org-extract-attributes link)))
   (setq link (if (string-match org-link-types-re link)
-		 (concat (match-string 1 link) ":"
+		 (concat (match-string 1 link)
 			 (org-link-escape (substring link (match-end 1))))
 	       (org-link-escape link)))
   (concat "[[" link "]"