Fix QuantumCircuit.compose with Index exprs (backport #12396)

[mergify]

Summary

This was an oversight in d6c74c2 (gh-12310), where an ExprVisitor was missed in the testing.

Details and comments

No release note because it's fixing an unreleased bug. I did another check for ExprVisitor classes in Qiskit, and all of them appear to be updated.

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This is an automatic backport of pull request #12396 done by Mergify.

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[coveralls]

Pull Request Test Coverage Report for Build 9080291033

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• 17 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.01%) to 89.623%

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Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/expr.rs	1	94.03%
qiskit/transpiler/passes/synthesis/unitary_synthesis.py	2	88.2%
crates/qasm2/src/lex.rs	2	92.37%
crates/qasm2/src/parse.rs	12	96.69%

Totals
Change from base Build 9033386902:	-0.01%
Covered Lines:	62252
Relevant Lines:	69460

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💛 - Coveralls