Remove fork chain checkpoints (2208000, 2209000) from mainnet

These checkpoints correspond to abandoned fork chains and are causing
IsInitialBlockDownload() to return TRUE incorrectly. The node at
height 2,207,881 is on the main chain but the code was requiring it
to sync to checkpoint 2,209,000 which doesn't exist on mainnet.

After this change, the highest mainnet checkpoint is 2,207,000,
which the node has already passed.

src/checkpoints.cpp

@@ -39,8 +39,6 @@ namespace Checkpoints
         {2205000, uint256("0xf7aa893ec012181e321783d6a5487addf6997377908faa3e760c9054a4217d29")},
         {2206000, uint256("0x780ae878f8b10b6cbd51ceb2c0799c90d3551fa916be62974375071b9e36581c")},
         {2207000, uint256("0x8836d67b0f08036c4a7c26ff0a29d4461a52b6d8f552165ad9c1abec2f3cadfd")},
-        {2208000, uint256("0xe4a19e8a29fa7aae47f7563377af3e896fee18ed069a64e325b8c2c6c820a1be")},
-        {2209000, uint256("0x04c78a6fc863bed918a9364c58c64489943b2e85d84ddb1ac2fba584f390d5dc")},
     };
 
     // Published UTXO snapshot file SHA256, keyed by snapshot height.