[identity] fix lastPrimarySignature attribute

Summary: While testing restore flow, I discovered device list validation on other clients is not passing, it's because we don't store `lastPrimarySignature` in DDB correctly.

Test Plan: N/A, just carefully reading code - I am going to test this with actual restore after deploying on staging

Reviewers: bartek, tomek

Reviewed By: bartek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D14079

services/identity/src/database/device_list.rs

@@ -633,7 +633,7 @@ impl From<DeviceListRow> for AttributeMap {
     }
     if let Some(last_signature) = device_list.last_primary_signature {
       attrs.insert(
-        ATTR_CURRENT_SIGNATURE.to_string(),
+        ATTR_LAST_SIGNATURE.to_string(),
         AttributeValue::S(last_signature),
       );
     }