fix(git): remove stale submodule index entries breaking scorecard #59

Job	Run time
governance / Well-Known (RFC 9116 + RSR)	9s
governance / Code quality + docs	25s
governance / Validate Hypatia baseline	9s
governance / Workflow security linter	6s
governance / Guix primary / Nix fallback policy	8s
governance / Trusted-base reduction policy	14s
governance / Licence consistency	8s
governance / Security policy checks	8s
governance / Language / package anti-pattern policy	1m 17s
	2m 44s

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