Old text in user_nl_cpl

Our user_nl_cpl has this text in it:
```
!------------------------------------------------------------------------
! Users should ONLY USE user_nl_cpl to change namelists variables
! for namelist variables in drv_in (except for the ones below) and
! any keyword/values in seq_maps.rc
! Users should add ALL user specific namelist and seq_maps.rc changes below
! using the following syntax
! namelist_var = new_namelist_value
! or
! mapname = new_map_name
! For example to change the default value of ocn2atm_fmapname to 'foo' use
! ocn2atm_fmapname = 'foo'
!
! Note that some namelist variables MAY NOT be changed in user_nl_cpl -
! they are defined in a $CASEROOT xml file and must be changed with
! xmlchange.
!
! For example, rather than set username to 'foo' in user_nl_cpl, call
! ./xmlchange USER=foo
!------------------------------------------------------------------------
```

I'm pretty sure the instructions about fmapname changes are wrong. Those have to be done with xmlchange because they are in env_run.xml.