[BUGFIX] indexed_search: fix marker documentation

Fix wrong marker example in sysext:indexed_search documentation.

Releases: master
Resolves: #71816
Change-Id: I967bf4c075df7e1771ddd8c424166214a458208d
Reviewed-on: https://review.typo3.org/44936


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>