Consitency of azimuthal angle name in RZ docstring (backport #13873)

[mergify]

• I have added the tests to cover my changes. (Doesn't apply ❌)
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.

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Summary:

Solves the 2nd part of Issue: #13871

But at least, what should 100% be done quickly, is make sure their documentation is consistent, for each gate, since there are cases where lambdas appear instead of thetas or phis... [check attached images]:

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This is an automatic backport of pull request #13873 done by [Mergify](https://mergify.com).

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[coveralls]

Pull Request Test Coverage Report for Build 13397124840

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 8 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.003%) to 88.929%

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Files with Coverage Reduction	New Missed Lines	%
crates/accelerate/src/two_qubit_decompose.rs	1	91.96%
crates/qasm2/src/lex.rs	7	92.23%

Totals
Change from base Build 13323858065:	0.003%
Covered Lines:	79183
Relevant Lines:	89041

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💛 - Coveralls