PDPVerifier still limits removals to 2000 per proving period

Now that we can support unbounded removal queue with user triggered queue flushing we should probably remove this global limit: https://github.com/FilOzone/pdp/blob/main/src/PDPVerifier.sol#L1001

Start in src/PDPVerifier.sol around line 1001 and trace how the 2000-removal limit relates to the user-triggered queue flushing mentioned in the issue. Remove the global per-proving-period cap so the removal queue can be unbounded, then verify that the surrounding queue-flushing behavior still works without that limit.

Written by the indexing model from the issue text.