should extra diffusivity`Kd_add`be added before we diagnose `Kd_work`

[raphaeldussin]

Kd_add is added to Kd after we diagnose the work (Kd * N2 * dz):

MOM6/src/parameterizations/vertical/MOM_set_diffusivity.F90

Line 671 in 31a4d8b

! Optionally add a uniform diffusivity to the layers.

shouldn't we invert the two so we diagnose the total work ?

[raphaeldussin]

solved by #765