docs: change images-service to nydus #2126

Job	Run time
nydus-build	2m 55s
contrib-build-master	1m 25s
contrib-build	1m 15s
nydus-build-master	2m 34s
nydus-unit-test	5m 41s
cargo-deny	6m 43s
nydus-unit-test-coverage	2m 56s
benchmark-nydus-no-prefetch-master	49s
benchmark-zran-all-prefetch-master	1m 28s
benchmark-nydus-filelist-prefetch-master	3m 54s
benchmark-nydus-all-prefetch-master	50s
benchmark-zran-no-prefetch-master	1m 24s
benchmark-oci	1m 23s
benchmark-zran-all-prefetch	1m 20s
benchmark-nydus-filelist-prefetch	3m 25s
benchmark-nydus-no-prefetch	40s
benchmark-zran-no-prefetch	1m 11s
nydus-integration-test	9m 16s
benchmark-nydus-all-prefetch	59s
benchmark-result	0s
benchmark-compare	24s
	50m 32s

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