build(deps): update opentelemetry-otlp requirement from 0.14.0 to 0.15.0 #126

Job	Run time
cargo check	34s
warnings	33s
cargo check (feature combinations)	18s
cargo check (+MSRV -Zminimal-versions) (1.65.0)	3m 35s
cargo fmt	6s
cargo check (+MSRV -Zminimal-versions) (stable)	21s
cargo test (stable on ubuntu-latest)	58s
build tests (wasm)	1m 2s
cargo test (beta on ubuntu-latest)	1m 2s
cargo test (nightly on ubuntu-latest)	1m 0s
cargo test (stable on windows-latest)	2m 57s
cargo test (stable on macos-latest)	1m 32s
all systems go!	0s
	13m 58s

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