Sync Gateway 2.7+ enable_shared_bucket_access references old import_docs behaviour

From: https://github.com/couchbase/sync_gateway/issues/4880

It looks like this was already reported at some point (DOC-6572), but I guess the changes have since been lost on the 2.7 and current versions of the doc config reference pages.

... in such a configuration where as import_docs can only be set to true on a single node.

2.7:

https://docs.couchbase.com/sync-gateway/2.7/config-properties.html#databases-foo_db-enable_shared_bucket_access

https://docs.couchbase.com/sync-gateway/2.7/config-properties.html#databases-foo_db-import_docs

Current (2.8):

https://docs.couchbase.com/sync-gateway/current/refer/config-properties.html#databases-this_db-enable_shared_bucket_access

https://docs.couchbase.com/sync-gateway/current/refer/config-properties.html#databases-this_db-import_docs