Comment 24 for bug 1846423

I am seeing this now with a CalDav calendar and Thunderbird 78.3.1
Relevant part from error console

```
Lightning: CalDAV: Unexpected status modifying item to RH: 403
BEGIN:VCALENDAR
PRODID:-//Mozilla.org/NONSGML Mozilla Calendar V1.1//EN
VERSION:2.0
BEGIN:VTIMEZONE
TZID:Europe/Warsaw
BEGIN:DAYLIGHT
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:19700329T020000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:19701025T030000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
END:STANDARD
END:VTIMEZONE
BEGIN:VTIMEZONE
TZID:Europe/London
BEGIN:DAYLIGHT
TZOFFSETFROM:+0000
TZOFFSETTO:+0100
TZNAME:BST
DTSTART:19700329T010000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0100
TZOFFSETTO:+0000
TZNAME:GMT
DTSTART:19701025T020000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
CREATED:20200513T135102Z
LAST-MODIFIED:20201008T092815Z
DTSTAMP:20201008T092815Z

......

X-LIC-ERROR:No value for LOCATION property. Removing entire property:
SEQUENCE:1
TRANSP:OPAQUE
X-MOZ-GENERATION:1
BEGIN:VALARM
ACTION:DISPLAY
TRIGGER;VALUE=DURATION:-PT10M
DESCRIPTION:This is an event reminder
X-LIC-ERROR;X-LIC-ERRORTYPE=PARAMETER-VALUE-PARSE-ERROR:Got a VALUE parameter with an illegal type for property: VALUE=DURATION
END:VALARM
END:VEVENT
BEGIN:VEVENT
CREATED:20200513T135102Z
LAST-MODIFIED:20201008T083606Z
DTSTAMP:20201008T083606Z
UID:<email address hidden>
SUMMARY:MW CPaaS Sync
STATUS:CONFIRMED
RECURRENCE-ID;TZID=Europe/Warsaw:20201019T110000
DTSTART;TZID=Europe/London:20201019T100000
DTEND;TZID=Europe/London:20201019T103000
END:VEVENT
```