ColGen: fix convergence condition

[guimarqu]

In some places, we check convergence as in the following method:

https://github.com/atoptima/Coluna.jl/blob/a2903a9803b44725797ef78defdc200c371259b7/src/Algorithm/colgen/default.jl#LL146C1-L146C136

This is not correct, because we should consider that the algorithm converged when the dual bound is equal or greater (resp lower) than the mlp in the minimization (resp maximization) case. Here, we only consider equality