minor bug scrolling calendar view

when scrolling calendar view, khal highlights the date below but leaves the previously selected still highlighted. very minor bug, probably very low priority as well but thought id leave this here :)

Steps to reproduce the behavior:
scroll when focused in calendar view

Expected behaviour:
should unhighlight the previously highlighted event, even when scrolling.

screenshot:

as you can see there are columns of dates selected in the calendar view :0

khal: version 0.13.0
python3: version 3.13.5
installed via: pacman (arch package manager)
Arch btw
config file:

[calendars]

[[personal]]
path = ~/.calendars/personal/
type = calendar
color = white

[[assignments]]
path = ~/.calendars/assignments/
type = calendar
readonly = True
color = light magenta

[[classes]]
path = ~/.calendars/classes/
type = calendar
readonly = True

[[exams]]
path = ~/.calendars/exams/
type = calendar
readonly = True

[locale]
timeformat = %H:%M
dateformat = %Y-%m-%d
longdateformat = %Y-%m-%d
datetimeformat = %Y-%m-%d %H:%M
longdatetimeformat = %Y-%m-%d %H:%M

[default]
default_calendar = personal
``

Reproduce the issue in khal's calendar view using the provided configuration, then trace how scrolling updates the highlighted date and event selection. The work is done when scrolling moves the highlight without leaving earlier dates or events highlighted, with the reported behavior covered by an appropriate test.