Bump oracle/oci from 6.20.0 to 6.21.0 in /terraform (#657)

Bumps [oracle/oci](https://github.com/oracle/terraform-provider-oci) from 6.20.0 to 6.21.0.
- [Release notes](https://github.com/oracle/terraform-provider-oci/releases)
- [Changelog](https://github.com/oracle/terraform-provider-oci/blob/master/CHANGELOG.md)
- [Commits](oracle/terraform-provider-oci@v6.20.0...v6.21.0)

---
updated-dependencies:
- dependency-name: oracle/oci
  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>

Author: dependabot[bot]