org-agenda.el: Remove any timestamp from the headline text.

* org-agenda.el (org-agenda-get-timestamps): Remove any
active timestamp from the headline text, not only those for
the current date.

Thanks to SW, Nick Dokos, Samuel Wales and Brian van den Broek
for inputs about this.

lisp/org-agenda.el

@@ -4982,13 +4982,7 @@ This function is invoked if `org-agenda-todo-ignore-deadlines',
 					     0 'org-hd-marker a))
 				   (cons (marker-position mm) a)))
 		  deadline-results))
-	 (remove-re
-	  (concat
-	   (regexp-quote
-	    (format-time-string
-	     "<%Y-%m-%d"
-	     (encode-time 0 0 0 (nth 1 date) (nth 0 date) (nth 2 date))))
-	   ".*?>"))
+	 (remove-re org-ts-regexp)
 	 (regexp
 	  (concat
 	   (if org-agenda-include-inactive-timestamps "[[<]" "<")