Bump @polkadot/api from 10.9.1 to 10.12.6

Bumps [@polkadot/api](https://github.com/polkadot-js/api/tree/HEAD/packages/api) from 10.9.1 to 10.12.6.
- [Release notes](https://github.com/polkadot-js/api/releases)
- [Changelog](https://github.com/polkadot-js/api/blob/master/CHANGELOG.md)
- [Commits](https://github.com/polkadot-js/api/commits/v10.12.6/packages/api)

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

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