Fix backslashes being accepted by `sanitizeArtifactName` #4887

Job	Run time
Ruby analysis (ubuntu-latest, linked)	46s
Ruby analysis (macos-latest, default)	1m 0s
Ruby analysis (macos-latest, linked)	1m 10s
Ruby analysis (ubuntu-latest, default)	47s
Ruby analysis (ubuntu-latest, nightly-latest)	47s
Ruby analysis (macos-latest, nightly-latest)	1m 18s
	5m 48s

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