[BUGFIX] Use proper quotation in phpdoc of ExtensionManagementUtility::addService()

The patch fixes the quotation in the description of the parameters
``$serviceType`` and ``$serviceKey``.
This ensures a correct rendering by Doxygen.

Resolves: #75283
Releases: master, 7.6, 6.2
Change-Id: Ic7d91c1c108465b50f7637667ff6f3a8b451eb26
Reviewed-on: https://review.typo3.org/47396


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>