Remove Subst.pred functionality #6779

Job	Run time
Java: Linting	1m 24s
Pyk: Code Quality & Unit Tests (3.10)	1m 24s
Pyk: Code Quality & Unit Tests (3.11)	1m 15s
Pyk: Code Quality & Unit Tests (3.12)	1m 20s
Code Quality Checks	1s
K: Ubuntu Jammy Package	21m 49s
K: Ubuntu Jammy Frontend Package	4m 4s
K: Nix Build & Test (self-hosted, linux, normal)	4m 19s
K: Source Build & Test	25m 42s
Pyk: Nix Build (ubuntu-latest)	37s
K: Nix Build & Test (MacM1, self-macos-12)	25m 41s
Pyk: Nix Build (macos-14)	1m 48s
Pyk: Integration Tests	17m 44s
Pyk: Documentation	3m 47s
Pyk: Profiling	3m 8s
Pyk: Regression Tests	17m 49s
	2h 11m 52s

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