[TASK] Superfluous comparison in InlineElement

Fix superfluous comparison against boolean in
InlineElement::renderForeignRecord().

Change-Id: I75bb1625ad7ead08e8e38fe46daa03071bc76113
Resolves: #54018
Releases: 6.2
Reviewed-on: https://review.typo3.org/25714
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters