range_tombstone_list: insert_from: correct rev.update range_tombstone in not overlapping case

2nd std::move(start) looks like a typo
in fe2fa3f20d.

Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Message-Id: <20220404124741.1775076-1-bhalevy@scylladb.com>
(cherry picked from commit 2d80057617)

Fixes ##10326

range_tombstone_list.cc

@@ -96,7 +96,7 @@ void range_tombstone_list::insert_from(const schema& s,
         if (cmp(end, it->position()) < 0) {
             // not overlapping
             if (it->tombstone().tomb == tomb && cmp(end, it->position()) == 0) {
-                rev.update(it, {std::move(start), std::move(start), tomb});
+                rev.update(it, {std::move(start), std::move(end), tomb});
             } else {
                 auto rt = construct_range_tombstone_entry(std::move(start), std::move(end), tomb);
                 rev.insert(it, *rt);