Revert "Avoid panic with recordsize > 128k, raw sending and no large_blocks"

This reverts commit 80a650b7bb04bce3aef5e4cfd1d966e3599dafd4. This change
inadvertently introduced a regression in ztest where one of the new ASSERTs
is triggered in dsl_scan_visitbp().

Reviewed-by: George Amanakis <gamanakis@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #12275
Closes #13799