Add link for backups

Author: jhamon

docs/upgrading.md

@@ -14,7 +14,7 @@ Some internals of the client have been reorganized or moved, but we've made an e
 New Features:
 - [Pinecone Assistant](https://www.pinecone.io/product/assistant/): The assistant plugin is now bundled by default. You can simply start using it without installing anything additional.
 - [Inference API](https://docs.pinecone.io/guides/get-started/overview#inference): List/view models from the model gallery via API
-- Backups:
+- [Backups](https://docs.pinecone.io/guides/manage-data/backups-overview):
   - Create backup from serverless index
   - Create serverless index from backup
   - List/view backups