chore(deps): update dependency node to v22.21.0 (#178)

This PR contains the following updates:

| Package | Type | Update | Change | OpenSSF |
|---|---|---|---|---|
| [node](https://redirect.github.com/actions/node-versions) | uses-with
| minor | `22.20.0` -> `22.21.0` | [![OpenSSF
Scorecard](https://api.securityscorecards.dev/projects/github.com/actions/node-versions/badge)](https://securityscorecards.dev/viewer/?uri=github.com/actions/node-versions)
|

---

### Release Notes

<details>
<summary>actions/node-versions (node)</summary>

###
[`v22.21.0`](https://redirect.github.com/actions/node-versions/releases/tag/22.21.0-18671149699):
22.21.0

[Compare
Source](https://redirect.github.com/actions/node-versions/compare/22.20.0-17993202319...22.21.0-18671149699)

Node.js 22.21.0

</details>

---

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This PR was generated by [Mend Renovate](https://mend.io/renovate/).
View the [repository job
log](https://developer.mend.io/github/settlemint/solidity-token-erc721a).

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<!-- This is an auto-generated description by cubic. -->
---

## Summary by cubic
Updates the Node.js version used in the Solidity GitHub Actions workflow
from 22.20.0 to 22.21.0. Keeps CI current and picks up upstream fixes.

<!-- End of auto-generated description by cubic. -->

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/solidity.yml

@@ -99,7 +99,7 @@ jobs:
 
       - uses: actions/setup-node@v4
         with:
-          node-version: 22.20.0
+          node-version: 22.21.0
 
       - name: Install Node dependencies
         run: npm install