fix: dev property should be in uppercase inside the env.json.sample file

[Dor-bl]

Change list

Currently our 'env.json.sample' contains the 'dev' property as Lowercase while our code is looking for 'DEV' in uppercase.

https://github.com/appium/appium-dotnet-driver/blob/6434b152860a2cf3ff52e41b3c6522ebe31db646/test/integration/helpers/Env.cs#L47-L51

What types of changes are you proposing/introducing to .NET client?
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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• New feature (non-breaking change which adds value to the project)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Documentation

• Have you proposed a file change/ PR with appium to update documentation?

This can be done by navigating to the documentation section on http://appium.io selecting the appropriate command/endpoint and clicking the 'Edit this doc' link to update the C# example

Integration tests

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Details

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[KazuCocoa]

Maybe you can already merge, correct? @Dor-bl You are in this repository's collaborator, in the settings

[Dor-bl]

@KazuCocoa Yes I am :)
I'll do it myself.(1st merge)
Thanks for the approval