build(deps): bump solana-nullable from 1.1.1 to 1.2.0 (#1284)

Bumps [solana-nullable](https://github.com/anza-xyz/solana-sdk) from 1.1.1 to 1.2.0.
- [Release notes](https://github.com/anza-xyz/solana-sdk/releases)
- [Commits](https://github.com/anza-xyz/solana-sdk/compare/nullable@v1.1.1...nullable@v1.2.0)

---
updated-dependencies:
- dependency-name: solana-nullable
  dependency-version: 1.2.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]