Fix highlight in ca2256 rule

[kurnakovv]

Summary

I made a mistake with the highlight position https://github.com/dotnet/docs/blob/main/docs/fundamentals/code-analysis/quality-rules/snippets/csharp/all-rules/ca2256.cs#L30

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Internal previews

📄 File	🔗 Preview link
docs/fundamentals/code-analysis/quality-rules/ca2256.md	CA2256: All members declared in parent interfaces must have an implementation in a DynamicInterfaceCastableImplementation-attributed interface

[gewarren]

Good catch -- thanks!