Fix weight windows regression test

[pshriwise]

Description

During evaluation of the current CI failure in #3751 I noticed that the weight windows intended to be applied to photons in the regression test were being applied to neutrons due to the lack specification for a particle type on the corresponding WeightWindows object.

This fixes that and takes care of a few more "while we're here items":

• removed some nuclides from the model material to reduce initialization time
• increased the number of particles run slightly
• added the collision checkpoint for weight windows

Like many of our regression tests, this is a very short run but I've confirmed from the tally results that the photons now do reach more mesh bins with weight windows turned on:

Neutrons

Analog

Weight Windows

Photons

Analog

Weight Windows

Checklist

• I have performed a self-review of my own code
• I have run [clang-format](https://docs.openmc.org/en/latest/devguide/styleguide.html#automatic-formatting) (version 15) on any C++ source files (if applicable)
• I have followed the style guidelines for Python source files (if applicable)
• I have made corresponding changes to the documentation (if applicable)
• I have added tests that prove my fix is effective or that my feature works (if applicable)

[GuySten]

Looks good to me.