Delete unused prdoc

prdoc/pr_7053.prdoc

-title: 'sync: Send already connected peers to new subscribers'
-doc:
-- audience: Node Dev
-  description: |-
-    Introduce `SyncEvent::InitialPeers` message sent to new subscribers to allow them correctly tracking sync peers. This resolves a race condition described in https://github.com/paritytech/polkadot-sdk/issues/6573#issuecomment-2563091343.
-
-    Fixes https://github.com/paritytech/polkadot-sdk/issues/6573.
-crates:
-- name: sc-network-gossip
-  bump: major
-- name: sc-network-statement
-  bump: patch
-- name: sc-network-sync
-  bump: major
-- name: sc-network-transactions
-  bump: patch