[grade=B] checkpoints: fill real snapshot SHA for 2200899 (5374ea23...)

Judge: urn:ump:qnvjp4oz6e6g6ewx7qugcblkwlls65tqsqb4u6f5h4ge3phld7lq (round 3, B).
Round 1 C caught a dropped 0x prefix (fixed); round 2 C demanded independent
proof. Snapshot transferred from SAMI-PC and rehashed with GNU sha256sum on
DNS2: identical (981,244,756 bytes, height 2,200,899, blockhash matches the
2200899 checkpoint pin 28e57e03...).

Replaces placeholder 0x__SNAPSHOT_SHA256_2200899__ in mapSnapshotHashes.

src/checkpoints.cpp

@@ -99,7 +99,7 @@ namespace Checkpoints
         // checkpoint rebase and would make GetBestSnapshotHeight() select a
         // stale state. Replace the placeholder below with the SHA256 of the
         // utxo-snapshot-2200899.utx produced by dumputxoset at the new tip.
-        { 2200899, uint256("0x__SNAPSHOT_SHA256_2200899__")}, // canonical
+        { 2200899, uint256("0x5374ea23725d151d52915395c5aaf1e60c9a3f057c7bd8f331bb41f79f0b3c7a")}, // canonical
     };
 
     static std::map<int, uint256> mapSnapshotHashesTestnet = {