Cold Storage: fix restore document with blob referenced by other documents

Steps to reproduce:

• create 2 documents with the exact same main content
• send the first one to cold storage and wait it is actually cold (glacier)
• Delete the blob from the glacier bucket (as if we had a real GC)
• observe the second document is also sent to cold storage OK (normal, since the main content blob is the same and is shared at storage level)
• Restore the first document (and wait it is restored)
• Go to the second document and observe it is still in cold storage KO (it should have been restored too since the main content blob is the same and is shared at storage level)
• When you click Restore from cold storage on the 2nd document, you get a toast message saying an error occurred and the document is stuck in a bad state

Expected result: the second document should have been automagically restored in a background task.