org-clock.el: Strip bracket links from the heading

* lisp/org-clock.el (org-clock--mode-line-heading): Strip
links from the heading.

This restores the previous behavior before commit 66554298.

Thanks to Matt Lundin for reporting this.

lisp/org-clock.el

@@ -518,7 +518,9 @@ cannot be translated."
   (cond ((functionp org-clock-heading-function)
 	 (funcall org-clock-heading-function))
 	((org-before-first-heading-p) "???")
-	(t (org-get-heading t t t t))))
+	(t (replace-regexp-in-string
+	    org-bracket-link-analytic-regexp "\\5"
+	    (org-no-properties (org-get-heading t t t t))))))
 
 (defun org-clock-menu ()
   (interactive)