Fix broken links to config_file in custom images docs #4159

Job	Run time
cargo-deny	23s
check	30s
fmt	11s
shellcheck	10s
clippy (macos-latest)	43s
test (macos-latest)	1m 20s
test (ubuntu-latest)	1m 18s
test (windows-latest)	2m 53s
clippy (ubuntu-latest)	26s
clippy (windows-latest)	1m 8s
generate-matrix	18s
bisect	6m 0s
docker-in-docker	3m 56s
foreign	2m 43s
podman	2m 10s
target (${{ matrix.pretty }},${{ matrix.os }})	0s
remote	2m 31s
publish	0s
conclusion	1s
Coverage	13s
	26m 54s

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