Revert "[TASK] Declare getThisScript() in ElementBrowser as public"

This reverts commit b2756fe7826d62fdc8442c887010890c268eabd8

A comment of Helmut Hummel was suggested, which was still missing.
This change will be repushed.

Releases: 6.2
Change-Id: I518af35f562350f9dde39678de52f69d58344677
Reviewed-on: https://review.typo3.org/28478
Reviewed-by: Markus Klein
Tested-by: Markus Klein