Rust: remove shipped feature flag #9981

Job	Run time
check-codeql-versions	53s
analyze-actions	1m 14s
analyze-javascript (ubuntu-22.04, linked)	4m 25s
analyze-javascript (ubuntu-24.04)	4m 14s
analyze-javascript (ubuntu-22.04)	4m 15s
analyze-javascript (ubuntu-24.04, linked)	4m 16s
analyze-javascript (windows-2022)	6m 44s
analyze-javascript (macos-13)	10m 13s
analyze-javascript (windows-2025)	7m 17s
analyze-javascript (macos-13, linked)	10m 19s
analyze-javascript (windows-2025, linked)	7m 24s
analyze-javascript (macos-15, linked)	10m 49s
analyze-javascript (macos-14, linked)	5m 55s
analyze-javascript (windows-2022, linked)	6m 47s
analyze-javascript (macos-14)	6m 33s
analyze-javascript (macos-15)	9m 3s
	1h 40m 21s

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