[CLEANUP] Cleanup code in ElementBrowser

This patch does not change functionality.
It just fixes formatting issues of the code and
corrects phpdoc.

Resolves: #53580
Releases: 6.2
Change-Id: I39a7ec757e6dfce8282053c3259a84edc2ba5588
Reviewed-on: https://review.typo3.org/25360
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Benjamin Mack
Tested-by: Benjamin Mack