.Net: Typo "Azure Open AI service key"→"Azure OpenAI Service Key" (mi…

…crosoft#2956)

### Motivation and Context

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### Description

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 Typo "Azure Open AI service key"→"Azure OpenAI Service Key"
https://github.com/microsoft/semantic-kernel/blob/main/dotnet/README.md
 #PingMSFTDocs

### Contribution Checklist

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- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows the [SK Contribution
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- [ ] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

---------

Co-authored-by: Dmytro Struk <[email protected]>

dotnet/README.md

@@ -4,8 +4,8 @@
 
 To run the LLM prompts and semantic functions in the examples below, make sure
 you have an
-[Open AI API Key](https://openai.com/api/) or
-[Azure Open AI service key](https://learn.microsoft.com/azure/cognitive-services/openai/quickstart?pivots=rest-api).
+[OpenAI API Key](https://openai.com/api/) or
+[Azure OpenAI Service Key](https://learn.microsoft.com/azure/cognitive-services/openai/quickstart?pivots=rest-api).
 
 ## Nuget package