fix: Use fromMnemonic instead of non-existent fromPhrase

[mdqst]

Description

I noticed that the code was using fromPhrase, which doesn't exist in the ethers library.
This has been corrected to use fromMnemonic for creating a wallet from a mnemonic phrase.

The change ensures compatibility with the library and resolves the issue.

[daveroga]

fromMnemonic function is not working in the current ethers version that we have in the project.
If we change fromPhrase to fromMnemonic we have an error:

const mnemonicWallet = ethers.Wallet.fromMnemonic(DEFAULT_MNEMONIC);
                                     ^
TypeError: hardhat_1.ethers.Wallet.fromMnemonic is not a function
    at Object.<anonymous> (/home/.../iden3/contracts/scripts/maintenance/multi-chain/checkIdTypes.ts:11:38)
    at Module._compile (node:internal/modules/cjs/loader:1358:14)
    at Module.m._compile (/home/.../iden3/contracts/node_modules/ts-node/src/index.ts:1618:23)
    at Module._extensions..js (node:internal/modules/cjs/loader:1416:10)
    at Object.require.extensions.<computed> [as .ts] (/home/.../iden3/contracts/node_modules/ts-node/src/index.ts:1621:12)
    at Module.load (node:internal/modules/cjs/loader:1208:32)
    at Function.Module._load (node:internal/modules/cjs/loader:1024:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:174:12)
    at node:internal/main/run_main_module:28:49