Update API usage in README.md

Author: kennethreitz

README.md

@@ -25,7 +25,7 @@ neon = NeonAPI(api_key='your_api_key')
 **[Documentation is available on ReadTheDocs](https://neon-api-python.readthedocs.io/)**.
 
 
-Remember that you should never expose your api_key and handle it carefully since it gives access to sensitive data. It's better to set it as an environment variable (e.g. `NEON_API_KEY` + accompanying `neon_client.from_environ()`).
+Remember that you should never expose your api_key and handle it carefully since it gives access to sensitive data. It's better to set it as an environment variable (e.g. `NEON_API_KEY` + accompanying `neon_api.from_environ()`).
 
 
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