chore(deps): update actions/checkout action to v2 (#77)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/checkout](https://togithub.com/actions/checkout) | action | major | `v1` -> `v2` |

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### Release Notes

<details>
<summary>actions/checkout</summary>

### [`v2`](https://togithub.com/actions/checkout/blob/master/CHANGELOG.md#v231)

[Compare Source](https://togithub.com/actions/checkout/compare/v1...v2)

-   [Fix default branch resolution for .wiki and when using SSH](https://togithub.com/actions/checkout/pull/284)

</details>

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.github/workflows/e2e-tests.yml

@@ -13,7 +13,7 @@ jobs:
       matrix:
         node-version: ['14.x']
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - name: Use Node.js
         uses: actions/setup-node@v2
         with: