[BUGFIX] Make extensionName parameter optional for LocalizationUtility::translate()

This patch prevents a PHP warning when second parameter of the method is not provided.
The extensionName is indeed optional since a fully qualified reference (starting with
"LLL:" may be provided as key.

Resolves: #81168
Releases: master, 8.7
Change-Id: I69145eb9379533b323696354d508b54bdbe4bd51
Reviewed-on: https://review.typo3.org/52741


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Henrik Elsner <helsner@dfau.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>