fix: hardhat-network-helpers and withdraw delay info (#226)

# Description

- Removes duplicated migration guide
- Updates info about hardhat-network-helpers plugin
- Updates info about withdraw delay and governance

## Linked Issues

N/A

## Additional context

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

@@ -34,13 +34,14 @@ You can learn more about each plugin in the [Getting started section](/build/too
 
     ::
 
-1. Import the plugin at the top of the `hardhat.config.ts` file:
+2. Import the plugin in the `hardhat.config.ts` file. If your project has multiple plugins, import `@matterlabs/hardhat-zksync` last:
 
     ```ts
+    // Other Hardhat plugin imports above
     import "@matterlabs/hardhat-zksync";
     ```
 
-1. Add the preferred ZKsync networks to the `hardhat.config.ts` file:
+3. Add the preferred ZKsync networks to the `hardhat.config.ts` file:
 
     ```js
     networks: {
@@ -197,8 +198,11 @@ ZKSync provides different EraVM node implementations to test smart contracts loc
 - In-Memory Node: fast L2 node with non-persistent state.
 - Dockerized setup: L1 and L2 nodes with persistent state but slower performance.
 
-::callout{icon="i-heroicons-information-circle" color="blue"}
 Unless your project contains L1-L2 features, testing with the In-Memory Node is recommended, which is included in the `@matterlabs/hardhat-zksync` plugin.
+
+::callout{icon="i-heroicons-exclamation-triangle" color="amber"}
+In version `1.0.12`, `hardhat-network-helpers` introduced support for both In-Memory Node and Dockerized setups, allowing methods
+such as `loadFixture` to be utilized in test files.
 ::
 
 You can read more about each node in the [Testing section of the docs](/build/test-and-debug).
@@ -210,10 +214,6 @@ To run tests using In-Memory Node, follow these steps:
 1. Add the `zksync:true` flag to the `hardhat` network in the `hardhat.config.ts` file to override Hardhat's default node with ZKsync In-Memory Node.
 1. Run the test task with `npx hardhat test --network hardhat` (or make `hardhat` the default network).
 
-::callout{icon="i-heroicons-exclamation-triangle" color="amber"}
-Methods from `hardhat-network-helpers` like `loadFixture` currently do not support testing with the In-Memory Node.
-::
-
 You can find more info about testing with the In-Memory-Node in [Hardhat-ZKsync node](/build/tooling/hardhat/plugins/hardhat-zksync-node#running-hardhats-test-task-with-hardhat-zksync-node).
 
 ### Running tests on Dockerized setup
@@ -404,7 +404,7 @@ 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();
 ```