website/docs: fix 2 links to cobalt restesting pdf #27898

Job	Run time
lint-golint	42s
test-unittest	3m 25s
ci-outpost-mark	2s
build-container (proxy)	3m 22s
build-binary (proxy, linux, amd64)	1m 59s
build-container (ldap)	2m 56s
build-binary (proxy, linux, arm64)	1m 50s
build-binary (ldap, linux, amd64)	2m 5s
build-container (radius)	2m 54s
build-binary (ldap, linux, arm64)	2m 2s
build-binary (radius, linux, amd64)	1m 39s
build-container (rac)	2m 54s
build-binary (radius, linux, arm64)	1m 50s
build-binary (rac, linux, amd64)	1m 35s
build-binary (rac, linux, arm64)	1m 56s
	31m 11s

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