[BUGFIX] Use non-deprecated name for filesPerPage option

Change the configuration name for the filesPerPage option in the file
list module from mod.file_list.filesPerPage to
options.file_list.filesPerPage because using "mod." in user TSconfig
is deprecated.

Resolves: #75976
Related: #72923
Releases: master
Change-Id: I13ad1a0f28b59ebe1fec7ccf4a73eaec0ddb0044
Reviewed-on: https://review.typo3.org/47966


Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Markus Sommer <markussom@posteo.de>
Tested-by: Markus Sommer <markussom@posteo.de>
Reviewed-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Tested-by: Jigal van Hemert <jigal.van.hemert@typo3.org>