Bump golang.org/x/tools from 0.20.0 to 0.21.0 (#55)

Bumps [golang.org/x/tools](https://github.com/golang/tools) from 0.20.0 to 0.21.0.
- [Release notes](https://github.com/golang/tools/releases)
- [Commits](golang/tools@v0.20.0...v0.21.0)

---
updated-dependencies:
- dependency-name: golang.org/x/tools
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Robert Pająk <[email protected]>