Fix repeated plots in docs (backport #13635)

[mergify]

Summary

The use of :context: in pages with several plots was causing an accumulation of figures, this PR fixes this issue by adding :context: close-figs. For example, the grover_operator docs before this PR showed:

While after the fix there is only one figure per snippet (as expected):

Details and comments

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This is an automatic backport of pull request #13635 done by [Mergify](https://mergify.com).

[qiskit-bot]

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1.4 has no commits so we probably shouldn't backport manually

[coveralls]

Pull Request Test Coverage Report for Build 12686854272

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.005%) to 88.93%

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Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/lex.rs	3	92.73%

Totals
Change from base Build 12350106200:	0.005%
Covered Lines:	79072
Relevant Lines:	88915

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💛 - Coveralls