Move snapshot/restore reference content to elasticsearch reference #1465
Description
Related to #1356
our self-managed repository types (and possibly other pages in the snapshot/restore section) act as reference content and contain client settings for snapshot repositories. we should pull the settings out of the tutorials if we can (without reducing the quality of the tutorial)
example page https://www.elastic.co/docs/deploy-manage/tools/snapshot-and-restore/s3-repository