build(deps): update opentelemetry-jaeger requirement from 0.20.0 to 0.21.0 #122

Job	Run time
cargo check	31s
cargo fmt	7s
cargo check (+MSRV -Zminimal-versions) (1.65.0)	3m 33s
cargo check (feature combinations)	27s
cargo check (+MSRV -Zminimal-versions) (stable)	25s
cargo test (stable on ubuntu-latest)	56s
build tests (wasm)	54s
cargo test (beta on ubuntu-latest)	1m 4s
warnings	54s
cargo test (nightly on ubuntu-latest)	1m 0s
cargo test (stable on windows-latest)	2m 25s
cargo test (stable on macos-latest)	1m 30s
all systems go!	0s
	13m 46s

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