fix: fix typo in migration guide for hh (#225)

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# Description
- should be upgradeBeacon instead of upgradeProxy 
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## Additional context

Author: dutterbutter

content/00.build/40.tooling/20.hardhat/20.migrating-to-zksync.md

@@ -405,7 +405,7 @@ await boxV2.waitForDeployment();
 ```typescript [hardhat-zksync-upgradeable]
 const upgradableProxyAddress = "UPGRADEABLE_PROXY_ADDRESS";
 const boxV2ContractFactory = await hre.ethers.getContractFactory("BoxV2");
-const boxV2 = await hre.upgrades.upgradeProxy(upgradableProxyAddress, boxV2ContractFactory);
+const boxV2 = await hre.upgrades.upgradeBeacon(upgradableProxyAddress, boxV2ContractFactory);
 await boxV2.waitForDeployment();
 ```