workaround Cholesky factorization limitations on v1.6

It won't handle adjoint but that makes it error even when its not used from the default choice, and so this makes it so the defaults don't error. Past v1.7 it's not needed.

Author: ChrisRackauckas

src/factorization.jl

@@ -260,13 +260,7 @@ function init_cacheval(alg::CholeskyFactorization, A::Matrix{Float64}, b, u, Pl,
     PREALLOCATED_CHOLESKY
 end
 
-function init_cacheval(alg::CholeskyFactorization, A::Diagonal, b, u, Pl, Pr,
-                       maxiters::Int, abstol, reltol, verbose::Bool,
-                       assumptions::OperatorAssumptions)
-    nothing
-end
-
-function init_cacheval(alg::CholeskyFactorization, A::AbstractSciMLOperator, b, u, Pl, Pr,
+function init_cacheval(alg::CholeskyFactorization, A::Union{Diagonal,AbstractSciMLOperator}, b, u, Pl, Pr,
                        maxiters::Int, abstol, reltol, verbose::Bool,
                        assumptions::OperatorAssumptions)
     nothing
@@ -281,7 +275,7 @@ end
     end
 
     function init_cacheval(alg::CholeskyFactorization,
-                           A::Adjoint{<:Array}, b, u, Pl, Pr,
+                           A::Adjoint{<:Number, <:Array}, b, u, Pl, Pr,
                            maxiters::Int, abstol, reltol, verbose::Bool,
                            assumptions::OperatorAssumptions)
         nothing