fix(http1): is_timeout works on HeaderTimeout #2896

Job	Run time
Verify hyper.h is up to date	24s
semver	14s
Check Style	7s
minimal-versions	37s
Test C API (FFI)	12s
Test with Miri	2m 36s
features	32s
Check MSRV	18s
Test stable on ubuntu-latest	1m 17s
udeps	22s
Test stable on windows-latest	2m 43s
Test stable on macOS-latest	1m 1s
Test beta on ubuntu-latest	1m 12s
Test beta on windows-latest	1m 50s
Test beta on macOS-latest	1m 13s
Test nightly on ubuntu-latest	1m 30s
Test nightly on windows-latest	2m 41s
Test nightly on macOS-latest	1m 42s
Check exposed types	15s
Build docs	19s
CI is green	0s
	21m 5s

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