[BUGFIX] ContentObjectRendereTest: Undefined constant NL

A data provider uses the not defined constant "NL". PHP 7.2
throws warnings on this. Warnings from data providers do not
lead to failing tests, still this is ugly and pollutes test
runs with warnings in the head part.

Change-Id: I3b09ce51d675cf3097967c074511eaf0a53cf8f9
Resolves: #83194
Releases: master, 8.7
Reviewed-on: https://review.typo3.org/54907


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>