The rf_rack_valid_keyspaces option needs to be turned on in order to
allow creating materialized views in tablet keyspaces with numeric RF
per DC. This is also necessary for secondary indexes because they use
materialized views underneath. However, this option is _not_ necessary
for vector store indexes because those use the external vector store
service for querying the list of keys to fetch from the main table, they
do not create a materialized view. The rf_rack_valid_keyspaces was, by
accident, required for vector indexes, too.
Remove the restriction for vector store indexes as it is completely
unnecessary.
Fixes: SCYLLADB-81
Closesscylladb/scylladb#27447
bb6e41f97a