Python: Update README.md to add clarity re: .env file (#10360)

clarified where to put the .env file

### Motivation and Context
As currently written, it's confusing as to where to put the .env file.
The proposed changes clarify where to put the .env file.

This improves onboarding experience and documentation.


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### Description
Minor changes to ReadMe to clarify where to put the .env file
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### 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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raises no violations
- [ ] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

Co-authored-by: Evan Mattson <[email protected]>

python/README.md

@@ -37,7 +37,9 @@ AZURE_OPENAI_ENDPOINT=""
 AZURE_OPENAI_API_KEY=""
 ```
 
-You will then configure the Text/ChatCompletion class with the keyword argument `env_file_path`:
+Put the .env file in the root directory.
+
+If you place the .env in a different directory, configure the Text/ChatCompletion class with the keyword argument `env_file_path`:
 
 ```python
 chat_completion = OpenAIChatCompletion(service_id="test", env_file_path=<path_to_file>)