Fix nesting prefixes in service API groups #4481

Job	Run time
check docs (ubuntu-latest / stable)	1m 5s
check feature flags (ubuntu-latest / stable)	16m 18s
check examples (ubuntu-latest / stable)	53s
check format (ubuntu-latest / nightly)	11s
check licenses (ubuntu-latest / stable)	24s
check linter (ubuntu-latest / stable)	1m 30s
check minimal versions of transitive dependencies (ubuntu-latest / stable)	1m 33s
check minimal supported rust version (ubuntu-latest / msrv)	47s
check spelling (ubuntu-latest / nightly)	5m 48s
test (ubuntu-latest / stable)	10m 59s
test (macos-latest / stable)	11m 59s
test (windows-latest / stable)	15m 12s
	1h 6m 39s

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