docs: Interface status colours show negative as positive & vice versa

[LukeFinch]

Describe the bug

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https://newskit.co.uk/theme/foundation/colours/

The common uses text for interfacePositive010 and interfaceNegative020 are mixed up

To Reproduce

Steps to reproduce the behavior:

https://newskit.co.uk/theme/foundation/colours/ - go to interface / status tab

Expected behavior

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Screenshots / Video / Test Environment

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Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context

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