[BUGFIX] Fix example code for TCA "fieldControl"

Resolves: #83732
Releases: master, 8.7
Change-Id: I7dccb42445dba584ed1c9a814f62525335d26ab1
Reviewed-on: https://review.typo3.org/55501


Reviewed-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Tested-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>