Update OpenZeppelin account artifacts to v0.2.1

[amanusk]

Updates OpenZeppelin account version to 0.2.1
Fixes #161

Usage related changes

• Use v0.2.1 of OpenZeppelin accounts

Development related changes

• Running npx hardhat test --no-compile test/oz-account-test.ts should now pass with both devnet and alpha-goerli

Checklist:

• Formatted the code
• No linter errors
• Tried to avoid introducing linter warnings
• Performed a self-review of the code
• Rebased to the last commit of the target branch (or merged it into my branch)
• Documented the changes
• Updated the test directory (with a test case consisting of network.json, hardhat.config.ts, check.sh)
• Linked issues which this PR resolves
• Created a PR to the plugin branch of starknet-hardhat-example:
  • < EXAMPLE_REPO_PR_URL >
  • Modified test.sh to use my example repo branch
  • Restored test.sh to to use the original branch (after the example repo PR has been merged)
• All tests are passing (for external contributors who don't have access to the CI/CD pipeline)

[FabijanC]

The ABI is the same as it was for 0.2.0?

[amanusk]

Yes, the ABI is the same. Checked with diff..

[FabijanC]

I'll approve & merge this when you can confirm that you successfully ran quick-test.ts and oz-account-test.ts from starknet-hardhat-example with this new account artifact.

[amanusk]

Tests are passing, and also running npm run test-general-tests is passing

[martriay]

Yes, the ABI is the same. Checked with diff..

Can confirm.