Bump ls-qpack from `b8d9fe7` to `a9fd921` #552

Job	Run time
Build (ubuntu, openssl, static, Debug)	2m 7s
Build (ubuntu, openssl, static, Release)	2m 13s
Build (ubuntu, openssl, shared, Debug)	2m 0s
Build (ubuntu, openssl, shared, Release)	2m 12s
Build (ubuntu, openssl3, static, Debug)	2m 50s
Build (ubuntu, openssl3, static, Release)	2m 39s
Build (ubuntu, openssl3, shared, Debug)	2m 42s
Build (ubuntu, openssl3, shared, Release)	2m 37s
Build (windows, schannel, static, Debug)	3m 5s
Build (windows, schannel, static, Release)	3m 57s
Build (windows, schannel, shared, Debug)	3m 42s
Build (windows, schannel, shared, Release)	3m 22s
Build (windows, openssl, static, Debug)	4m 59s
Build (windows, openssl, static, Release)	5m 4s
Build (windows, openssl, shared, Debug)	4m 37s
Build (windows, openssl, shared, Release)	5m 4s
Build (windows, openssl3, static, Debug)	5m 20s
Build (windows, openssl3, static, Release)	5m 48s
Build (windows, openssl3, shared, Debug)	5m 50s
Build (windows, openssl3, shared, Release)	6m 26s
Build Complete	4s
	1h 16m 38s

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