Now that issues #7586 and #9487 were fixed, reverse queries - even in long partitions - work well, we can drop the claim in alternator/docs/compatibility.md that reverse queries are buggy for large partitions. We can also remove the "xfail" mark from the tes that checks this feature, as it now passes. Refs #7586 Refs #9487 Signed-off-by: Nadav Har'El <nyh@scylladb.com> Closes #9831