Fix mypy errors (scheduler)

[Randl]

Summary

Following discussion, I'm splitting #8187 by module.

Details and comments

There are two errors left:

qiskit/scheduler/lowering.py:91: error: Incompatible types in assignment (expression has type "Union[int, ParameterExpression]", target has type "int")  [assignment]
qiskit/scheduler/lowering.py:96: error: Incompatible types in assignment (expression has type "List[int]", variable has type "Tuple[int, ...]")  [assignment]

The first is quite common and is related mostly to parametric expressions: indices of channels can technically be ParameterExpression but I believe in this case index is supposed to be int?

The second is inconsistency between two branches of if where in first qubits is a tuple and in second is a list. Since it is not modified, the solution is probably to change it to tuple (I've added todo in the relevant line)

[qiskit-bot]

Thank you for opening a new pull request.

Before your PR can be merged it will first need to pass continuous integration tests and be reviewed. Sometimes the review process can be slow, so please be patient.

While you're waiting, please feel free to review other open PRs. While only a subset of people are authorized to approve pull requests for merging, everyone is encouraged to review open pull requests. Doing reviews helps reduce the burden on the core team and helps make the project's code better for everyone.

One or more of the the following people are requested to review this:

• @Qiskit/terra-core

[coveralls]

Pull Request Test Coverage Report for Build 5058923131

• 7 of 7 (100.0%) changed or added relevant lines in 2 files are covered.
• 6 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.02%) to 85.89%

---

Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/expr.rs	1	93.76%
crates/qasm2/src/lex.rs	5	90.89%

Totals
Change from base Build 5050064110:	0.02%
Covered Lines:	70924
Relevant Lines:	82575

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 7375421297

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.007%) to 87.56%

---

Totals
Change from base Build 7369683756:	0.007%
Covered Lines:	59260
Relevant Lines:	67679

---

💛 - Coveralls

[jakelishman]

Sorry this never merged at the time. This stuff got removed in Qiskit 2.0, so the PR is obsolete.