Remove eflx_grnd_lake restart field

It looks like this is no longer needed. This was added to the restart
file in clm4_5_1_r105 (cf8a5e0), presumably to fix the different fill
patterns upon restart that are mentioned in #31. However,
there was a later change that seems to fix this issue the correct way,
by ensuring that eflx_grnd_lake is set in every time step, rather than
potentially persisting at its previous value (in clm4_5_13_r204 -
ce9e407; see also the discussion in
http://bugs.cgd.ucar.edu/show_bug.cgi?id=1717).

Note that eflx_grnd_lake is just a diagnostic field: it doesn't appear
on the right-hand side of any equations in the model.

src/biogeophys/EnergyFluxType.F90

@@ -876,11 +876,6 @@ subroutine Restart(this, bounds, ncid, flag, is_simple_buildtemp, is_prog_buildt
          long_name='instantaneous daily minimum of transpiration wetness factor', units='', &
          interpinic_flag='interp', readvar=readvar, data=this%btran_min_inst_patch) 
 
-    call restartvar(ncid=ncid, flag=flag, varname='eflx_grnd_lake', xtype=ncd_double,  &
-         dim1name='pft', &
-         long_name='net heat flux into lake/snow surface, excluding light transmission', units='W/m^2', &
-         interpinic_flag='interp', readvar=readvar, data=this%eflx_grnd_lake_patch)
-
     call this%eflx_dynbal_dribbler%Restart(bounds, ncid, flag)
 
   end subroutine Restart