[BUGFIX] Title includes html tags

In the filelist special folders like _temp_ and _recycler_ folder are
highlighted in bold as they get human readable names. The <strong>
tags are shown in the title tag as well. Therefore the title tag has
to be stripped of any html tags.

Change-Id: I4b21a916851e0d02aa58971eabda32f813bd890c
Fixes: #46532
Releases: 6.1, 6.0
Reviewed-on: https://review.typo3.org/19167
Reviewed-by: Fabien Udriot
Reviewed-by: Michael Staatz
Reviewed-by: Oliver Klee
Tested-by: Michael Staatz
Reviewed-by: Wouter Wolters
Reviewed-by: Andreas Wolf
Tested-by: Andreas Wolf