Fix symbol conversion into qiskit

[cqc-alec]

Description

Fix the conversion of symbols from pytket circuits to qiskit so that round-trip equality checks pass.

This needs qiskit >= 1.2.0 to work, so bump the minimum qiskit version.

Related issues

Fixes #376 .

Checklist

• I have performed a self-review of my code.
• I have commented hard-to-understand parts of my code.
• I have made corresponding changes to the public API documentation.
• I have added tests that prove my fix is effective or that my feature works.
• I have updated the changelog with any user-facing changes.

[cqc-melf]

We should bump up the pytket version, too.
Do you want to do that in this PR?

[cqc-alec]

We should bump up the pytket version, too. Do you want to do that in this PR?

I was thinking to do that in a separate PR.