- Remove bottom blank space on the right column of the calendar popover
so that the weather card is bottom-aligned with the clear button on
the left column.
- Remove top blank space on the left column of the calendar popover so
that the message list is top-aligned with the today button on the
right column.
- Adjust .message-list-controls sizing to align with other card-styled
elements.
- Use regular `spacing` instead of margin for some spacing.
https://gitlab.gnome.org/GNOME/gnome-shell/issues/2088
Closes https://gitlab.gnome.org/GNOME/gnome-shell/issues/2120