[BUGFIX] Remove last usage of show_item.php

Use getModuleUrl instead.

Resolves: #68783
Releases: master
Change-Id: I8ce3e3b9801c87e96669ba5870450c974efde26c
Reviewed-on: http://review.typo3.org/42304


Reviewed-by: Susanne Moog <typo3@susannemoog.de>
Tested-by: Susanne Moog <typo3@susannemoog.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>