Rust: remove shipped feature flag #5050

Job	Run time
Ruby analysis (macos-latest, default)	1m 14s
Ruby analysis (macos-latest, linked)	1m 5s
Ruby analysis (ubuntu-latest, linked)	47s
Ruby analysis (ubuntu-latest, nightly-latest)	50s
Ruby analysis (macos-latest, nightly-latest)	1m 22s
Ruby analysis (ubuntu-latest, default)	49s
	6m 7s

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