Remove limit for number of availability rules

[Valentina R]

There seem to be a limit of 55 rules. Adding new ones wont save to DB.

Can be reproduced here: https://fable.valentina-rakar.com/wp-admin/post.php?post=14381&action=edit

Reported here: https://bookingwp.com/forums/topic/issues-with-plugin/

[Valentina R]

Increasing post_max_size does not help.

[Željan Topić]

Duplicate of #518.