[BUGFIX] No duplicate html encoding in file titles

This patch makes sure that UserFileInlineLabelService only parses the
title of a file through htmlspecialchars if this was not already done by
a BackendUtility method like getRecordTitle() or getRecordTitlePrep().

Titles that are cropped by getRecordTitlePrep() will be displayed
correctly in the Backend.

Resolves: #53200
Releases: 6.2
Change-Id: I960e599372aeecfb2e5e6469ac4d644c578cfabc