Remove unused HCFcoretype setting

[mgjarrett]

Description

The HCFcoretype setting is not used anywhere in the framework or in downstream TerraPower projects.

Since the only options are TWR*, I assume nobody outside of TerraPower is using this setting either.

TerraPower TH solvers use an assembly parameter to track hot channel factors:

armi/armi/reactor/assemblyParameters.py

Lines 358 to 366 in 0576560

	pb.defParam(
	"hotChannelFactors",
	units="None",
	description="Definition of set of HCFs to be applied to assembly.",
	location="?",
	default="Default",
	saveToDB=True,
	categories=[parameters.Category.assignInBlueprints],
	)

I assume anybody else wanting to apply hot channel factors would want to use the same assembly parameter, and not this case setting.

---

Checklist

• This PR has only one purpose or idea.
• Tests have been added/updated to verify that the new/changed code works.

• The code style follows good practices.
• The commit message(s) follow good practices.

• The release notes (location doc/release/0.X.rst) are up-to-date with any bug fixes or new features.
• The documentation is still up-to-date in the doc folder.
• The dependencies are still up-to-date in setup.py.

[mgjarrett]

The coverage reduction is from two uncovered lines here:

armi/armi/runLog.py

Lines 649 to 651 in 0576560

	except FileExistsError:
	# If we hit this race condition, we still win.
	return

I don't know how we were hitting the FileExistsError before, or how we could force it to be hit again. It's not clear how it relates to this PR.

[opotowsky]

Nice cleanup catch! Somehow I missed it when investigating the HCF settings...

That is a weird reason for a coverage drop. Sometimes it happens if the base branch isn't perfectly in sync with main, and even though github is smart enough to handle that situation, coveralls might not be.