Improve docstring for unitary() & other text in unitary_protocol.py #19907

Job	Run time
Packaging test	1m 32s
Misc check	6s
Changed files test	1m 59s
Doc test	1m 37s
Notebook formatting	13s
Type check	1m 24s
Format check	16s
Lint check	2m 29s
Shell check	9s
Isolated pytest Ubuntu	7m 19s
Pytest Ubuntu (3.11)	9m 11s
Typescript tests coverage	32s
Check consistency of requirements	18s
Pytest Ubuntu (3.13)	10m 19s
Coverage check	17m 5s
Pytest Ubuntu (3.12)	9m 50s
Changed Notebooks Isolated Test against Cirq stable (partition-0)	59s
Changed Notebooks Isolated Test against Cirq stable (partition-2)	54s
Notebook Tests against PR	8m 32s
Changed Notebooks Isolated Test against Cirq stable (partition-1)	57s
Pytest Windows (3.13)	11m 24s
Typescript lint check	38s
Pytest Windows (3.11)	10m 3s
Pytest Windows (3.12)	11m 10s
Changed Notebooks Isolated Test against Cirq stable (partition-3)	57s
Typescript tests	45s
Pytest MacOS (3.13)	6m 37s
Pytest MacOS (3.12)	12m 43s
Pytest MacOS (3.11)	10m 30s
Bundle file consistency	32s
Build protos	26s
	2h 21m 26s

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