fix(http1): fix intermitent panic parsing partial headers #2931

Job	Run time
semver	2m 28s
Verify hyper.h is up to date	31s
Check Style	26s
features	30s
Test C API (FFI)	40s
Test cargo-c support (FFI)	11s
minimal-versions	31s
Test with Miri	2m 45s
Check MSRV	35s
udeps	24s
Test stable on ubuntu-latest	1m 12s
Test stable on windows-latest	3m 30s
Test stable on macOS-latest	1m 4s
Test beta on ubuntu-latest	1m 9s
Test beta on windows-latest	1m 57s
Test beta on macOS-latest	1m 22s
Test nightly on ubuntu-latest	1m 20s
Test nightly on windows-latest	2m 40s
Test nightly on macOS-latest	1m 41s
Check exposed types	14s
Build docs	21s
CI is green	1s
	25m 32s

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