fixup! fix: replace Zygote adjoint with ChainRulesCore adjoint

Author: AayushSabharwal

ext/SciMLBaseZygoteExt.jl

@@ -40,37 +40,6 @@ import SciMLStructures
     VA[i, j], ODESolution_getindex_pullback
 end
 
-# @adjoint function Base.getindex(VA::ODESolution, sym, j::Int)
-#     function ODESolution_getindex_pullback(Δ)
-#         i = symbolic_type(sym) != NotSymbolic() ? variable_index(VA, sym) : sym
-#         du, dprob = if i === nothing
-#             getter = getobserved(VA)
-#             grz = pullback(getter, sym, VA.u[j], VA.prob.p, VA.t[j])[2](Δ)
-#             du = [k == j ? grz[2] : zero(VA.u[1]) for k in 1:length(VA.u)]
-#             dp = grz[3] # pullback for p
-#             if dp === nothing
-#                 dp = zeros(size(parameter_values(VA)))
-#                 dp = parameter_values(VA)
-#             end
-#             dprob = remake(VA.prob, p = dp)
-#             du, dprob
-#         else
-#             du = [m == j ? [i == k ? Δ : zero(VA.u[1][1]) for k in 1:length(VA.u[1])] :
-#                   zero(VA.u[1]) for m in 1:length(VA.u)]
-#             dp = zero(VA.prob.p)
-#             dprob = remake(VA.prob, p = dp)
-#             du, dprob
-#         end
-#         T = eltype(eltype(VA.u))
-#         N = ndims(VA)
-#         Δ′ = ODESolution{T, N}(du, nothing, nothing,
-#             VA.t, VA.k, VA.discretes, dprob, VA.alg, VA.interp, VA.dense, 0, VA.stats,
-#             VA.alg_choice, VA.retcode)
-#         (Δ′, nothing, nothing)
-#     end
-#     VA[sym, j], ODESolution_getindex_pullback
-# end
-
 @adjoint function EnsembleSolution(sim, time, converged, stats)
     out = EnsembleSolution(sim, time, converged, stats)
     function EnsembleSolution_adjoint(p̄::AbstractArray{T, N}) where {T, N}