chat: fix stale CRITICAL comment in saveConnInfo

Comment claimed SEDBException is re-thrown as CRITICAL but only
SEDBBusyError is (via the `critical` helper at Subscriber.hs:136
and the showCritical branch at :1695). Updated to describe the actual
behaviour.

src/Simplex/Chat/Library/Subscriber.hs

@@ -368,8 +368,9 @@ processAgentMessageConn :: VersionRangeChat -> User -> ACorrId -> ConnId -> AEve
 processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage = do
   -- Missing connection/entity errors here will be sent to the view but not shown as CRITICAL alert,
   -- as in this case no need to ACK message - we can't process messages for this connection anyway.
-  -- SEDBException will be re-trown as CRITICAL as it is likely to indicate a temporary database condition
-  -- that will be resolved with app restart.
+  -- SEDBBusyError will be re-thrown as CRITICAL (via `critical`) as it indicates a transient lock/IO
+  -- condition that usually resolves after app restart. Other SEDBException flavours surface as
+  -- non-CRITICAL store errors.
   entity <- critical agentConnId $ withStore (\db -> getConnectionEntity db vr user $ AgentConnId agentConnId) >>= updateConnStatus
   case agentMessage of
     END -> case entity of