Address minor issues identified in 10/24 Code Audit

[andrewlee94]

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Fixes None

Summary/Motivation:

The developer team did a code audit in October and identified a number of issues that should be investigated and resolved if possible. This PR addresses those issues that are easily fixed.

Changes proposed in this PR:

• Update CODEOWNERS file in light of staffing changes
• Add condition to xfail marker on plate heat exchanger tests to only xfail on Windows system.

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