DOCSP-14227 -- update OM backup flow diagram (#791)

- [DOCSP-number](https://jira.mongodb.org/browse/DOCSP-14227)
-
[STAGING](https://deploy-preview-791--docs-ops-manager.netlify.app/core/backup-overview/)

### Self-Review Checklist

- [ ]
[Define](https://wiki.corp.mongodb.com/display/DE/Taxonomy+tagging+instructions)
taxonomy
[values](https://wiki.corp.mongodb.com/display/DE/Docs+Taxonomy) at top
of page.
- [ ] Add genre facets (tutorial or reference), as in this [example
PR](10gen/cloud-docs#5042).
- [ ] Add programmingLanguage (if necessary).
- [ ] Add meta keywords (if necessary).
- [ ] Resolve any new warnings or errors in the build.
- [ ] Proofread for spelling and grammatical errors.
- [ ] Check staging for rendering issues.
- [ ] Confirm links are working.

Author: jvincent-mongodb