refactor(common): remove unused H2Stream stub #2210

Job	Run time
Verify hyper.h is up to date	54s
Check Style	15s
features	30s
Check MSRV	4m 9s
Test with Miri	1m 53s
Test C API (FFI)	1m 4s
udeps	31s
Test stable on ubuntu-latest	2m 23s
Test stable on windows-latest	4m 44s
Test stable on macOS-latest	1m 41s
Test beta on ubuntu-latest	2m 13s
Test beta on windows-latest	3m 25s
Test beta on macOS-latest	2m 42s
Test nightly on ubuntu-latest	2m 16s
Test nightly on windows-latest	4m 18s
Test nightly on macOS-latest	1m 46s
Check exposed types	31s
Build docs	28s
CI is green	1s
	35m 44s

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