Protocol-Test: Remove unnecessary MAX_INV Limit to MAX_MESSAGE test / Or replace.

The following Test found in
https://github.com/bcoin-org/bcash/blob/master/test/protocol-test.js#L151

The GetDataPacket size values to 1800003
Whilst the current updated MAX_MESSAGE value is 2097152

There is a possibility of changing the typeof invitems, or simply removing the test I'd be willing to hear out what is the better option. So that I can replace or remove the check in the test file for ci purposes.

Start in test/protocol-test.js around line 151 and compare the GetDataPacket size values with the current MAX_MESSAGE value of 2097152. Decide whether the outdated check should be replaced or removed, then run the protocol test and CI to confirm the test suite passes.

Written by the indexing model from the issue text.