[FOLLOWUP][BUGFIX] Improve domObjectId splitting for inline in flexform

Thanks to activated strict typing in FormInlineAjaxController the
third parameter of removeFromArray is not accepted anymore. Declared
the right type it works again.

Resolves: #76268
Relates: #73004
Releases: master
Change-Id: I9404e7e6ee97ccdf00e77caf1e78f8baa060cd26
Reviewed-on: https://review.typo3.org/48528


Reviewed-by: Susanne Moog <typo3@susannemoog.de>
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Susanne Moog <typo3@susannemoog.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Jan Helke <typo3@helke.de>
Tested-by: Jan Helke <typo3@helke.de>