comment min_area references

[ahijevyc]

Avoid ValueError: not enough values to unpack (expected 4, got 3)

Correct the number of arguments expected from pipelines in make_GLM_grids.py by removing references to min_flash_area_grid and min_area_grid.

Traceback (most recent call last):
  File "make_GLM_grids.py", line 329, in <module>
    gridder(glm_filenames, start_time, end_time, **grid_kwargs)
  File "/glade/scratch/ahijevyc/glmtools/glmtools/grid/make_grids.py", line 838, in grid_GLM_flashes
    outputs = list(map(this_proc_each_grid, subgrids))
  File "/glade/scratch/ahijevyc/glmtools/glmtools/grid/make_grids.py", line 877, in proc_each_grid
    gridder = GLMGridder(start_time, end_time, **kwargsij)
  File "/glade/u/home/ahijevyc/miniconda3/envs/glmval/lib/python3.6/site-packages/lmatools/grid/make_grids.py", line 202, in __init__
    self.pipeline_setup()
  File "/glade/scratch/ahijevyc/glmtools/glmtools/grid/make_grids.py", line 239, in pipeline_setup
    ) = flash_outgrids
ValueError: not enough values to unpack (expected 4, got 3)