Switch from the chrono `clock` feature to `now` #4297

Job	Run time
lint	3m 49s
non-default-examples (opentelemetry-otlp/examples/basic-otlp)	44s
external-types (opentelemetry)	1m 4s
external-types (opentelemetry-sdk)	1m 13s
test (stable)	7m 20s
cargo-deny	24s
test (beta)	7m 9s
docs	1m 32s
msrv	4m 32s
coverage	3m 32s
	31m 19s

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