Fixes typo on api/qiskit/providers page

[LeanderCS]

Summary

Fixes #13211

Fixed typo on the api/qiskit/providers page where the QuantumCircuit variable qc was incorrectly called as c.

No tests are needed.

Details and comments

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[coveralls]

Pull Request Test Coverage Report for Build 11241388480

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 166 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.01%) to 88.86%

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Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/expr.rs	1	94.02%
crates/qasm2/src/lex.rs	5	91.48%
crates/qasm2/src/parse.rs	12	96.69%
crates/circuit/src/operations.rs	148	89.43%

Totals
Change from base Build 11225763971:	-0.01%
Covered Lines:	74737
Relevant Lines:	84106

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💛 - Coveralls

[ElePT]

Thanks for your contribution. We typically don't add release notes for documentation fixes, so my only comment is that I'd remove the release note.

[LeanderCS]

Thanks for your contribution. We typically don't add release notes for documentation fixes, so my only comment is that I'd remove the release note.

Thanks, didn't know it.
I will do it right away.

[ElePT]

LGTM!