Relax now-unneeded constraints

[jakelishman]

Summary

These were added in #7174 and #7815. Both Matplotlib and Sphinx have been updated several times since then, and should now be compatible.

Details and comments

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[coveralls]

Pull Request Test Coverage Report for Build 3290571596

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 142 unchanged lines in 5 files lost coverage.
• Overall coverage decreased (-0.2%) to 84.57%

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Files with Coverage Reduction	New Missed Lines	%
qiskit/extensions/quantum_initializer/squ.py	2	79.78%
qiskit/pulse/library/waveform.py	3	91.49%
src/results/marginalization.rs	29	71.84%
src/sampled_exp_val.rs	49	6.56%
src/sabre_swap/mod.rs	59	80.94%

Totals
Change from base Build 3290531884:	-0.2%
Covered Lines:	61818
Relevant Lines:	73097

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💛 - Coveralls