When viewing a datagrid in mobile mode, we were absolute-positioning the

filter dropdown to the right. This used to be fine, since we were

restricting the size of the title text, but the recent move to flexbox

changed that, resulting in the elements overlapping.
Fortunately, we can just take advantage of that flexbox and get rid of

the absolute positioning.

Tested the datagrid filter display at varying widths, making sure that

wrapping was always correct.