DetailsList: aria-selected is always present, even if SelectionMode.None is specified

[abettadapur]

Bug Report

• Package version(s): (fill this out) Latest

Priorities and help requested (not applicable if asking question):

Are you willing to submit a PR to fix? (Yes, No) No

Requested priority: (Blocking, High, Normal, Low) Normal

Describe the issue:

DetailsRow will always apply the aria-selected attribute, even if the selectionmode is set to SelectionMode.None. This results in extraneous information being read to screen reader users in certain scenarios and situations.

Actual behavior:

Screenreaders read "not-selected", even if selection is disabled

Expected behavior:

The attribute should not be present, and screenreaders should not read any selection information if SelectionMode is set to none