scraping_method-overview.ipynb: add a Warning not to run selenium in Colab?

[DanilSko]

The selenum part in scraping_method-overview.ipynb fails due to non-existent Chrome binary (which makes total sense).

WebDriverException: Message: unknown error: cannot find Chrome binary

Should we nevertheless warn the user?

[hsluytergaethje]

The selenium part is only a toy example, the website is not real, that is requested. I made this clearer in the notebook now. I am not sure what info to add about the execution in colab though, how would you warn them?