docs: Add use citation from HH at HL-LHC paper

[matthewfeickert]

Description

Add use citation from Double Higgs production at the HL-LHC: probing a loop-enhanced model with kinematical distributions by Leandro Da Rold, Manuel Epele, Anibal D. Medina, Nicolás I. Mileo, Alejandro Szynkman.

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• Tests are passing
• "WIP" removed from the title of the pull request
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* Add use citation from 'Double Higgs production at the HL-LHC: probing
  a loop-enhanced model with kinematical distributions'.
   - c.f. https://inspirehep.net/literature/2739283

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9a0d285) 98.28% compared to head (77028c4) 98.28%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2407   +/-   ##
=======================================
  Coverage   98.28%   98.28%           
=======================================
  Files          69       69           
  Lines        4539     4539           
  Branches      803      803           
=======================================
  Hits         4461     4461           
  Misses         45       45           
  Partials       33       33           

Flag	Coverage Δ
contrib	97.86% <ø> (ø)
doctest	60.71% <ø> (ø)
unittests-3.10	96.29% <ø> (ø)
unittests-3.11	96.29% <ø> (ø)
unittests-3.8	96.32% <ø> (ø)
unittests-3.9	96.34% <ø> (ø)

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[matthewfeickert]

Relevant RTD build: https://pyhf--2407.org.readthedocs.build/en/2407/citations.html#use-citations