Release 2.1.0: Drop Python 3.7 Support and Loosen Z3 Requirements

This release drops support for Python 3.7 (in accordance with its deprecation in Qiskit).
Furthermore, it drops the variable limitation in the exact mapper allowing to explore larger circuits and architectures.

What's Changed

• 🐍🔥 Drop Python 3.7 support by @burgholzer in #224
• 🔥 Drop variable limitation for exact mapper by @burgholzer in #225

Full Changelog: v2.0.1...v2.1.0