Pin Qiskit to <2 in next release

[edoaltamura]

Summary

Pinning Qiskit<2 will avoid breaking changes to affect current installations. This potential effect was raised in #897. The constraint can be removed when QML achieves full compatibility with Qiskit 2.

[woodsp-ibm]

I am wondering - in the requirements.txt already exists a version limit for qiskit

qiskit>=1.0
scipy>=1.4
numpy>=1.17
scikit-learn>=1.2
setuptools>=40.1
dill>=0.3.4

Would it be better to keep the version restrictions in one place especially since its a direct dependent i.e. qiskit>=1.0,<2.0. I also notice that there is a version limiting on numpy while the constraints.txt has something different.

[coveralls]

Pull Request Test Coverage Report for Build 13954831611

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 90.857%

---

Totals
Change from base Build 13954824039:	0.0%
Covered Lines:	4482
Relevant Lines:	4933

---

💛 - Coveralls

[woodsp-ibm]

Just a comment to this:

The constraint can be removed when QML achieves full compatibility with Qiskit 2.

Before this it has a constraint >=1.0 so that rather than being removed (depending in what removed is exactly) the upper bound could be removed but that's likely then to become the lower bound i.e. >=2.0 I would think.