RGS `Update had same timestamp as last processed update` shouldn't be an error

[TheBlueMatt]

See lightningdevkit/rapid-gossip-sync-server#17 but this just shouldn't be an error, we should probably try to apply anyway, though.

[G8XSU]

I will take this up,
BOLT: "MUST set timestamp to be greater than that of any previous node_announcement it has previously created."
And we should re-broadcast if new timestamp in received msg is greater.

Doubt: If we remove this check, we might apply and broadcast a few duplicate gossips. (non-rgs case)
is that fine?

Concern is when we receive same msg from multiple nodes.

[TheBlueMatt]

The timestamp here is the one set by the RGS server (roughly "when the snapshot was generated"), not one connected to network messages themselves, so there's no relevant BOLT requirements here.