crosstab documentation should add a note about use in materialized views

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/15/tablefunc.html
Description:

When using a crosstab in a materialized view, if the SQL is not qualified
with a schema, that restoring a database from a dump may fail. See the
discussion in
https://www.postgresql.org/message-id/16202-b6b345c9d2819409%40postgresql.org