Remove ZYgote from deps

Author: Alex Robson

Project.toml

@@ -9,7 +9,6 @@ LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 PDMats = "90014a1f-27ba-587c-ab20-58faa44d9150"
 SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 SuiteSparse = "4607b0f0-06f3-5cda-b6b1-a6196a1729e9"
-Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [compat]
 ChainRulesCore = "1"