[BUGFIX] Remove leftover info about config.uniqueLinkVars

Remove obsolete info about a removed setting in tsref.xml
and remove one duplicate `to` just two lines later.

Resolves: #79208
Related: #62888
Releases: master, 7.6
Change-Id: I4c2a437edb657eb380ffb2377947977a850da497
Reviewed-on: https://review.typo3.org/51204
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Frans Saris <franssaris@gmail.com>
Tested-by: Frans Saris <franssaris@gmail.com>