Add reference values for Met Office H(x) calculation

[BenjaminRuston]

Add reference values for Met Office H(x) calculation (without super-refraction check)

is required for https://github.com/JCSDA-internal/ufo/pull/3117

Description

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Issue(s) addressed

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Impact

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Checklist

• [ ] I have performed a self-review of my own code
• [ ] I have made corresponding changes to the documentation
• [ ] I have run the unit tests before creating the PR

[BenjaminRuston]

@neill-b or @fcvdb anyone want to review this? then can merge the associated UFO PR

[BenjaminRuston]

@neill-b may need you to fix this! so you and @hailingz were updating the same test file?