Pin qiskit_sphinx_theme version

[mtreinish]

The recently released 1.11.x release series of the sphinx theme is incompatible with the customization we made to the templates for the theme to remove the top bar. The recommendation from the theme package maintainers was to just pin the theme version to the old version if the modifications are required. This should unblock the CI docs failure we've seen for the past couple of weeks which was caused by an incompatibility with our template files.

Longer term, I think we might want to migrate to a different theme package for the rustworkx docs. The direciton of the qiskit docs theme is to be more tightly coupled with the evolving Qiskit ecosystem which makes a lot of sense for the other consumers of the theme package. But for rustworkx we typically have tried to keep it independent as it's a base dependency for Qiskit, so selecting a different theme is probably the best path forward to avoid tension like this in the future.

[coveralls]

Pull Request Test Coverage Report for Build 4916829034

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.01%) to 97.071%

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Files with Coverage Reduction	New Missed Lines	%
src/shortest_path/all_pairs_dijkstra.rs	2	98.54%

Totals
Change from base Build 4731978762:	-0.01%
Covered Lines:	14385
Relevant Lines:	14819

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💛 - Coveralls

[mtreinish]

Superseded by #867