Updating cluster settings

[mbk-tp]

What is the change?

• Removing the setting mpiTasksPerNode
• Renaming numProcessors to nTasks

Why is the change being made?

Updating terminology to something more modern.

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Checklist

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

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

• The release notes have been updated if necessary.
• The documentation is still up-to-date in the doc folder.
• The dependencies are still up-to-date in pyproject.toml.

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2 out of 3 committers have signed the CLA.

✅ john-science
✅ mbk-tp
❌ Bharat Medasani

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[john-science]

Can you add a release not here: https://github.com/terrapower/armi/blob/main/doc/release/0.4.rst?plain=1#L42

It should says "Renaming numProcessors to nTasks".