Fix new test for clocktables

* testing/lisp/test-org-clock.el (test-org-clock/clocktable): The last test
  for clocktables introduced in commit 6642177 did not work if the test was
  run before 15:00 due to the end time being specified as "<now>" (which
  includes the current time of day and not just the date).  The obvious
  "<today>" does also not work since it means 0:00 of the current day.  The
  correct specification to use is "<tomorrow>", which is 0:00 the following
  day or equivalently the end of today, 24:00.

testing/lisp/test-org-clock.el

@@ -145,7 +145,7 @@ contents.  The clocktable doesn't appear in the buffer."
 	(goto-char (point-min))
 	(forward-line)
 	(test-org-clock-clocktable-contents-at-point
-	 ":tstart \"<yesterday>\" :tend \"<now>\" :indent nil"))))))
+	 ":tstart \"<yesterday>\" :tend \"<tomorrow>\" :indent nil"))))))
 
 
 (provide 'test-org-clock)