Bump polkadot-api from 1.20.7 to 1.21.0

Bumps [polkadot-api](https://github.com/polkadot-api/polkadot-api) from 1.20.7 to 1.21.0.
- [Release notes](https://github.com/polkadot-api/polkadot-api/releases)
- [Changelog](https://github.com/polkadot-api/polkadot-api/blob/main/NEWS.md)
- [Commits](https://github.com/polkadot-api/polkadot-api/compare/[email protected]@1.21.0)

---
updated-dependencies:
- dependency-name: polkadot-api
  dependency-version: 1.21.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package.json

@@ -39,7 +39,7 @@
     "copy-to-clipboard": "^3.3.3",
     "lucide-react": "^0.554.0",
     "next-themes": "^0.4.6",
-    "polkadot-api": "^1.20.7",
+    "polkadot-api": "^1.21.0",
     "react": "^19.2.0",
     "react-dom": "^19.2.0",
     "react-icons": "^5.5.0",