document http.sslCertType and sslKeyType #22429

Job	Run time
config	6s
fuzz smoke test	37s
win+VS build	0s
sparse	3m 32s
static-analysis	3m 58s
win build	3m 51s
almalinux-8 (almalinux:8)	3m 47s
debian-11 (debian:11)	3m 46s
linux32 (i386/ubuntu:focal)	3m 46s
linux-musl (alpine)	3m 46s
pedantic (fedora)	1m 39s
documentation	3m 57s
linux-asan-ubsan (ubuntu-latest)	3m 58s
win+VS test	0s
linux-gcc (ubuntu-20.04)	3m 59s
linux-gcc-default (ubuntu-latest)	3m 57s
linux-leaks (ubuntu-latest)	3m 58s
linux-meson (ubuntu-latest)	4m 0s
linux-reftable (ubuntu-latest)	3m 59s
linux-reftable-leaks (ubuntu-latest)	3m 42s
linux-sha256 (ubuntu-latest)	3m 16s
linux-TEST-vars (ubuntu-20.04)	3m 32s
osx-clang (macos-13)	3m 55s
osx-gcc (macos-13)	2m 28s
osx-meson (macos-13)	2m 13s
osx-reftable (macos-13)	1s
win test	0s
	1h 15m 43s

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