chore: set 3.0 mainnet activation height

Author: kantai

stackslib/src/core/mod.rs

@@ -97,7 +97,7 @@ pub const BITCOIN_MAINNET_STACKS_24_BURN_HEIGHT: u64 = 791_551;
 /// This is Epoch-2.5, activation height proposed in SIP-021
 pub const BITCOIN_MAINNET_STACKS_25_BURN_HEIGHT: u64 = 840_360;
 /// This is Epoch-3.0, activation height proposed in SIP-021
-pub const BITCOIN_MAINNET_STACKS_30_BURN_HEIGHT: u64 = 2_000_000;
+pub const BITCOIN_MAINNET_STACKS_30_BURN_HEIGHT: u64 = 867_867;
 
 pub const BITCOIN_TESTNET_FIRST_BLOCK_HEIGHT: u64 = 2000000;
 pub const BITCOIN_TESTNET_FIRST_BLOCK_TIMESTAMP: u32 = 1622691840;