It was introduced to get newer File Picker dialogs (i#70927)
but the special manifest file for that was not actually used for years;
LO 3.5 already includes a generic manifest file that is like any other
and probably has zero benefit over the manfiest that is embedded in
the soffice.bin binary anyway.

Change-Id: I0f41f10ecf26201043a8c9964cdfef95bc348eb8