Update pnpm/action-setup action to v4 (#156)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [pnpm/action-setup](https://togithub.com/pnpm/action-setup) | action |
major | `v2.4.0` -> `v4.0.0` |

---

### Release Notes

<details>
<summary>pnpm/action-setup (pnpm/action-setup)</summary>

###
[`v4.0.0`](https://togithub.com/pnpm/action-setup/releases/tag/v4.0.0)

[Compare
Source](https://togithub.com/pnpm/action-setup/compare/v3.0.0...v4.0.0)

An error is thrown if one version of pnpm is specified in the
`packageManager` field of `package.json` and a different version is
specified in the action's settings
[#&#8203;122](https://togithub.com/pnpm/action-setup/pull/122)

###
[`v3.0.0`](https://togithub.com/pnpm/action-setup/releases/tag/v3.0.0)

[Compare
Source](https://togithub.com/pnpm/action-setup/compare/v2.4.0...v3.0.0)

The action is updated to run on Node.js v20

</details>

---

### Configuration

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are satisfied.

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rebase/retry checkbox.

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---

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---

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.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
     - name: Checkout
       uses: actions/checkout@v4
     - name: Install pnpm
-      uses: pnpm/action-setup@v2.4.0
+      uses: pnpm/action-setup@v4.0.0
       with:
         version: 8
     - name: Install Node.js