LP1867524: Add a help popover to the End field in the Closed Dates Editor

LP1867524: Add a help popover to the End field in the Closed Dates Editor

To test:
1) Go to Administration > Local Administration > Closed Dates Editor.
2) Click Add Closing.
3) Under closing type, choose Multiple Day.
4) Note that the End field has no guidance for the user.
5) Apply this commit.
6) Repeat steps 1-3.
7) Notice that the End field has some clarifying guidance for the user.

Signed-off-by: Jane Sandberg <sandbej@linnbenton.edu>
Signed-off-by: Mike Risher <mrisher@catalyte.io>
Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>