Remove note in MOM_override

[anton-seaice]

We should remove this note in MOM_override:

! WARNING: DO NOT EDIT this file! Any user change made in this file will be
!          overriden. This file is automatically generated. MOM6 parameter
!          changes may be made via SourceMods or user_nl_mom.
!-------------------------------------------------------------------------

Its a hangover from CIME / CESM, not related to us. Users can add to this file as they like !