doc: Add matrix expressions to docstrings #2394

Job	Run time
build (ubuntu-latest, 3.9, amazon-braket-pennylane-plugin-python)	3m 10s
build (ubuntu-latest, 3.10, amazon-braket-pennylane-plugin-python)	3m 9s
build (ubuntu-latest, 3.11, amazon-braket-pennylane-plugin-python)	3m 7s
build (macos-latest, 3.9, amazon-braket-pennylane-plugin-python)	4m 39s
build (macos-latest, 3.10, amazon-braket-pennylane-plugin-python)	3m 51s
build (macos-latest, 3.11, amazon-braket-pennylane-plugin-python)	3m 58s
build (windows-latest, 3.9, amazon-braket-pennylane-plugin-python)	5m 55s
build (windows-latest, 3.10, amazon-braket-pennylane-plugin-python)	5m 55s
build (windows-latest, 3.11, amazon-braket-pennylane-plugin-python)	6m 44s
	40m 28s

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