Missing weight windows for fng_str

[paulromano]

I noticed when trying to run openmc_model.py on the fng_str model that the weight windows referenced there are missing:

openmc_fusion_benchmarks/models/fng_str/openmc_model.py

Lines 2184 to 2186 in 8dd3e60

	settings.weight_windows = openmc.wwinp_to_wws("ww_heating.cadis.wwinp")
	else:
	settings.weight_windows = openmc.wwinp_to_wws("ww_rr.cadis.wwinp")

In the folder, there is a weight_windows.cadis.wwinp file.

[SteSeg]

Yes, I was play around with separate neutrons and photons ww files but I met a bug with the heating results (bug solved here openmc PR #3227) and I probably left the wrong files.

I am working now on cleaning up this benchmark. In the meanwhile you can switch to this file weight_windows.cadis.wwinp. It works just fine in all the runs.