chore: remove unnecessary black_box in criterion #654

Job	Run time
msrv-check	49s
compat-integration-test-instrumentation (-p codspeed-bencher-compat)	1m 52s
lint	1m 0s
compat-integration-test-instrumentation (--features async_futures -p codspeed-criterion-compat)	2m 3s
tests	9m 13s
compat-integration-test-instrumentation (-p codspeed-divan-compat-examples)	3m 21s
compat-integration-test-instrumentation (-p codspeed)	1m 42s
compat-integration-test-walltime (codspeed-divan-compat-examples)	4m 30s
compat-integration-test-instrumentation (-p codspeed-divan-compat)	1m 58s
compat-integration-test-walltime (codspeed-divan-compat)	3m 45s
compat-integration-test-walltime (codspeed-criterion-compat)	10m 49s
check	2s
	41m 4s

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