Re-enable Nonconvex in OPF benchmarks

[ChrisRackauckas]

Identified in #735, symbolic = true caused the server to halt:

_bk;t=1694823702792Internal error: stack overflow in type inference of (::RuntimeGeneratedFunctions.RuntimeGeneratedFunction{(:ˍ₋arg1,), Symbolics.var"#_RGF_ModTag", Symbolics.var"#_RGF_ModTag", (0xaa552898, 0xaf8490d0, 0x20badbf9, 0xf8e30c84, 0x637debea), Expr})(Array{Symbolics.Num, 1}).

_bk;t=1694828646696This might be caused by recursion over very long tuples or argument lists.

_bk;t=1694828646696Internal error: stack overflow in type inference of (::RuntimeGeneratedFunctions.RuntimeGeneratedFunction{(:ˍ₋arg1,), Symbolics.var"#_RGF_ModTag", Symbolics.var"#_RGF_ModTag", (0xaa552898, 0xaf8490d0, 0x20badbf9, 0xf8e30c84, 0x637debea), Expr})(Array{Float64, 1}).

_bk;t=1694828656064This might be caused by recursion over very long tuples or argument lists.

_bk;t=1694828656064Internal error: stack overflow in type inference of (::RuntimeGeneratedFunctions.RuntimeGeneratedFunction{(:ˍ₋arg1,), Symbolics.var"#_RGF_ModTag", Symbolics.var"#_RGF_ModTag", (0xccb40d2a, 0x291b25aa, 0xb313de73, 0xc2fe367a, 0x85a9f745), Expr})(Array{Symbolics.Num, 1}).

_bk;t=1694828679462This might be caused by recursion over very long tuples or argument lists.

_bk;t=1694828679462Internal error: stack overflow in type inference of (::RuntimeGeneratedFunctions.RuntimeGeneratedFunction{(:ˍ₋arg1,), Symbolics.var"#_RGF_ModTag", Symbolics.var"#_RGF_ModTag", (0xccb40d2a, 0x291b25aa, 0xb313de73, 0xc2fe367a, 0x85a9f745), Expr})(Array{Float64, 1}).

_bk;t=1694830468077This might be caused by recursion over very long tuples or argument lists.

_bk;t=1694830468077

while false caused

Error: MethodError: no method matching Float64(::ForwardDiff.Dual{ForwardDiff.Tag{NonconvexUtils.var"#101#108"{NonconvexUtils.var"#100#107"{NonconvexUtils.var"#97#104"{NonconvexCore.VectorOfFunctions{Vector{NonconvexCore.IneqConstraint{var"300", Float64, Int64, Set{Symbol}} where var"300"<:Function}}}}}, Float64}, Float64, 1})

Closest candidates are:
  (::Type{T})(::Real, !Matched::RoundingMode) where T<:AbstractFloat
   @ Base rounding.jl:207
  (::Type{T})(::T) where T<:Number
   @ Core boot.jl:792
  (::Type{T})(!Matched::AbstractChar) where T<:Union{AbstractChar, Number}
   @ Base char.jl:50
  ...

Thus there's some bug in Nonconvex that needs to be fixed before it can be re-enabled, otherwise it stops all benchmarks above a certain size.