Update qiskit/circuit/__init__.py (typo corrected) (backport #13203)

[mergify]

Summary

Corrected the typo while I was going through the docs to solve some other issue.
link to section where type is - link

Details and comments

In the 3rd paragraph, "you cannot use a gate in a definition it its own definition depends on the parent." should be replaced by "you cannot use a gate in a definition if its own definition depends on the parent."

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This is an automatic backport of pull request #13203 done by [Mergify](https://mergify.com).

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[coveralls]

Pull Request Test Coverage Report for Build 10966486053

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 11 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.007%) to 89.764%

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Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/expr.rs	1	94.02%
crates/qasm2/src/lex.rs	4	92.98%
crates/qasm2/src/parse.rs	6	97.15%

Totals
Change from base Build 10964920105:	0.007%
Covered Lines:	66881
Relevant Lines:	74508

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💛 - Coveralls