Refactor README.md. Remove instructions for setting environment varia…

…bles and mention that max context length depends on the model used.

README.md

@@ -31,10 +31,11 @@
     ```
 
 - Set the environment variable `OPENAI_API_KEY` to your OpenAI API key.
-- By default, model max content length is set to `4097` tokens (max length for `gpt-3.5-turbo`). If you want to use a different model with a different max length, set the environment variable `OPENAI_MODEL_MAX_LENGTH` to the max length of the model you want to use.
 
 - By default, Painy will use the `gpt-3.5-turbo` (ChatGPT), if you want to use a different model, set the environment variable `OPENAI_MODEL_NAME` to the model you want to use. You must have access to the model you want to use.
 
+- Max context length depends on the model you use. Try to use the tool on not too big changes, ideally on a single file.
+
 ## Usage
 
 - (Recommended) Go to the folder with your repository and run the following command: