Fix display of checkboxes in Pale Moon

In Pale Moon (24.7.1) the checkboxes in the file list are not in the responding line on the icon but all of them are next to the "select all" checkbox.
This fix should not change anything in Firefox and chromium (on windows) but as the comment states it has to be checked on KDE/Qt.
BTW why is position absolute naccessary? For my understanding relative is exactly what you want to use in such a case...
remove obsolete code comment
Merge pull request #10271 from miicha/patch-2

Fix display of checkboxes in Pale Moon