Style Guide: Fix two-letter acronym
Style Guide: Fix two-letter acronym

The old text was based on what was in the [Dart guideline](https://dart.dev/guides/language/effective-dart/style#do-capitalize-acronyms-and-abbreviations-longer-than-two-letters-like-words) and was not adjusted in the PR when we changed our inspiration to be the [.NET guideline](https://docs.microsoft.com/en-us/dotnet/standard/design-guidelines/capitalization-conventions) -- (it was only changed in the examples in our internal discussion)
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