BREAK: deprecate `sphinxcontrib-hep-pdgref` package (#32) #21

Job	Run time
pytest / Determine job matrix	7s
style / Determine skipped pre-commit hooks	13s
pytest / Run unit tests (3.10, ubuntu-22.04)	28s
pytest / Run unit tests (3.11, ubuntu-22.04)	36s
pytest / Run unit tests (3.7, ubuntu-22.04)	31s
pytest / Run unit tests (3.9, ubuntu-22.04)	35s
pytest / Run unit tests (3.6, ubuntu-20.04)	46s
pytest / Run unit tests (3.8, ubuntu-22.04, sphinxcontrib)	32s
pytest / Run unit tests (3.9, macos-12)	53s
style / Run taplo through pre-commit	38s
style / Run local pre-commit hooks	1m 12s
style / Push changes	0s
	6m 31s

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