[TASK] Label "Online Users" label in EXT: beusers label

Change label from "Active Sessions" to "Online Users"
in backend user administration module.

Also fixes bug in HTML table.

Resolves: #62181
Releases: master
Change-Id: Iafd2398f019455033816b5f3d2a26020761acd91
Reviewed-on: http://review.typo3.org/33283
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Reviewed-by: Stefan Froemken <froemken@gmail.com>
Tested-by: Stefan Froemken <froemken@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>