Restore the batch size kludge for attribution

ipa-core/src/protocol/ipa_prf/prf_sharding/mod.rs

@@ -510,7 +510,9 @@ where
             protocol: &Step::Attribute,
             validate: &Step::AttributeValidate,
         },
-        chunk_size,
+        // TODO: this should not be necessary, but probably can't be removed
+        // until we align read_size with the batch size.
+        std::cmp::min(sh_ctx.active_work().get(), chunk_size),
     );
     dzkp_validator.set_total_records(TotalRecords::specified(histogram[1]).unwrap());
     let ctx_for_row_number = set_up_contexts(&dzkp_validator.context(), histogram)?;