Also removes the default limit of 1000, which was too low to hold more
than ~3h of L1 data. This was causing problems whenever a duration of 3h
has passed since a latest batch was posted, which then caused derivation
of a new batch to fetch all L1 data again.
This particularly impacted chains that have a usual channel duration
longer than 3h, or when chains experienced a safe head stall >3h.

Fixes #13409.