Clean up Polarfire code references

[tvami]

Is your feature request related to a problem? Please describe.

I just learned what Polarfire was supposed to be, and now I understand we wont do anything with it. However, there are references and code about it in ldmx-sw: https://github.com/search?q=repo%3ALDMX-Software%2Fldmx-sw%20polarfire&type=code

Describe the solution you'd like

Clear these up?

Describe alternatives you've considered

They arent actually doing any harm so could just do nothing too...