This patch adds the missing warning about the lack of possibility
to return the similarity distance. This will be added in the next
iteration.
Fixes #27086
It has to be backported to 2025.4 as this is the limitation in 2025.4.
Closes scylladb/scylladb#27096
(cherry picked from commit f714876eaf)
Closes scylladb/scylladb#27105