Last day of month (L) does not work in tandem with other days of month

[glemoine-intouch]

Having trouble with this cron expression:

0 23 L,15 * *

This is a valid cron expression (Last day of the month AND 15th of the month), but is being validated as false by this line https://github.com/dragonmantank/cron-expression/blob/master/src/Cron/DayOfMonthField.php#L142

If you remove this line, it appears to work just fine, and produces next run dates as you'd expect. Any reason why this extra validation exists, and if not could it be removed and/or modified to allow expressions like the above to validate?

[aGervaisIntouch]

Bump