Fix repeated plots in docs

[ElePT]

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

[qiskit-bot]

One or more of the following people are relevant to this code:

• @Cryoris
• @Qiskit/terra-core
• @ajavadia

[coveralls]

Pull Request Test Coverage Report for Build 12675002826

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 9 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.004%) to 88.94%

---

Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/lex.rs	3	92.73%
crates/qasm2/src/parse.rs	6	97.62%

Totals
Change from base Build 12670558519:	-0.004%
Covered Lines:	79442
Relevant Lines:	89321

---

💛 - Coveralls

[jakelishman]

Wow, in some ways I'm surprised that this is the default behaviour. I guess I can just about see the purpose if you're showing how a plot builds up in the matplotlib documentation, but for most uses, it seems like close-figs should be the default.

[ElePT]

@Mergifyio backport stable/1.4

[mergify]

backport stable/1.4

✅ Backports have been created

• #13639 Fix repeated plots in docs (backport #13635) has been created for branch stable/1.4

[ElePT]

@Mergifyio backport stable/1.3

[mergify]

backport stable/1.3

✅ Backports have been created

• #13640 Fix repeated plots in docs (backport #13635) has been created for branch stable/1.3