Bump version to 1.2.0

[uri-granta]

Related issue(s)/PRs:

Summary

Bump version to 1.2.0 in preparation for release.

Fully backwards compatible: yes

PR checklist

• [x] The quality checks are all passing
• [ ] The bug case / new feature is covered by tests
• [ ] Any new features are well-documented (in docstrings or notebooks)