Radius not recognized in LMTR

[MaxenceGollier]

RegularizedOptimization.jl/src/LMTR_alg.jl

Line 427 in 84f3d1e

update_bounds!(l_bound_m_x, u_bound_m_x, false, l_bound, u_bound, xk, ∆k)

For some reason when the algorithm reaches this line, the radius is not recognized and we get the error

LoadError: UndefVarError: `∆k` not defined in `RegularizedOptimization`

It is very surprising that the tests did not catch that, i think the ∆ just has the wrong encoding (it should be Δ which apparently is not the same).