[TASK] Remove not evaluated JavaScript property fsMod.currentMainLoaded

This property is unevaluated since TYPO3 6.1

Resolves: #78537
Releases: master
Change-Id: Id5decd6d06b05bfc2c13b35870a8576d4b461b52
Reviewed-on: https://review.typo3.org/50481


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