This commit removes the Apache copyright note from the Cassandra Stress page. It's a follow up to https://github.com/scylladb/scylladb/pull/21723, which missed that update (see https://github.com/scylladb/scylladb/pull/21723#discussion_r1944357143). Cassandra Stress is a separate tool with separate repo with the docs, so the copyright information on the page is incorrect. Fixes https://github.com/scylladb/scylladb/issues/23240 Closes scylladb/scylladb#24219