Update 07_RAG_Generator.md

[CarterT27]

Fixed a grammatical error in the tutorial md file

[anakin87]

Hello @CarterT27!

Thanks for the contribution.

To modify to the tutorials, you should edit the ipynb notebook then generate the updated markdown files as specified here.

Probably it was not very clear. @bilgeyucel is currenty improving the contributing guide (#119).

[TuanaCelik]

This was fixed, and we made the contribution process simpler so that you don't have to generate markdowns, simply edit the .ipynb :) thanks for the fix!