Symmetry of the double Riesz pressure components

The mixed second derivative realization identifies the two index orders.

theorem CKN.Leray.rieszPressureOperator_ae_eq_index_swap (r : ℝ) (hr : 1 < r) (i j : Fin 3) (g : Foundation.Parabolic.Vec3 → ℝ) (hg : MeasureTheory.MemLp g (ENNReal.ofReal r) MeasureTheory.volume) (hg2 : MeasureTheory.MemLp g 2 MeasureTheory.volume) : (fun (x : Foundation.Parabolic.Vec3) => ↑↑((rieszPressureOperator r hr i j) (MeasureTheory.MemLp.toLp g hg)) x) =ᵐ[MeasureTheory.volume] fun (x : Foundation.Parabolic.Vec3) => ↑↑((rieszPressureOperator r hr j i) (MeasureTheory.MemLp.toLp g hg)) x

CKN's two all-exponent pressure components agree in their index order, used by lem:riesz-duality.