updated the link for OpenAI API (openai#400)

* just updated the url for OpenAi API

* updated the docs

Author: Someet-Git

openai/util.py

@@ -184,5 +184,5 @@ def default_api_key() -> str:
         return openai.api_key
     else:
         raise openai.error.AuthenticationError(
-            "No API key provided. You can set your API key in code using 'openai.api_key = <API-KEY>', or you can set the environment variable OPENAI_API_KEY=<API-KEY>). If your API key is stored in a file, you can point the openai module at it with 'openai.api_key_path = <PATH>'. You can generate API keys in the OpenAI web interface. See https://onboard.openai.com for details, or email [email protected] if you have any questions."
+            "No API key provided. You can set your API key in code using 'openai.api_key = <API-KEY>', or you can set the environment variable OPENAI_API_KEY=<API-KEY>). If your API key is stored in a file, you can point the openai module at it with 'openai.api_key_path = <PATH>'. You can generate API keys in the OpenAI web interface. See https://platform.openai.com/account/api-keys for details, or email [email protected] if you have any questions."
         )