fix(protocol): std leaking into tests #722

Job	Run time
doctest	53s
no-std	40s
wasm-unknown	1m 6s
test stable --no-default-features	47s
test stable	1m 13s
wasm-wasi	1m 11s
cfg-check	20s
test stable --all-features	1m 51s
test nightly --no-default-features	32s
clippy	43s
docs	22s
test nightly	1m 13s
examples	59s
test nightly --all-features	1m 43s
feature-checks	2m 56s
feature-powerset	8m 53s
test 1.81 --no-default-features	37s
fmt	12s
test 1.81	51s
	27m 2s

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