Fix typo in python requirements filename

[singhay]

No description provided.

[mbrochh]

Hi there, thank you for the pull request. I'm not quite sure if this is correct, thought? First of all, there are no changes in the requirements.txt file, secondly, you changed the graphiql endpoint to be called graphql, but I named it graphiql, including the i, on purpose, because that is how the web-based editor is called.

[singhay]

Hi @mbrochh ,

1. The name of the file is backend/requiremets.txt → backend/requirements.txt there is an n missing in requiremets.txt so when people copy paste code from repo readme, they get an IO error that file not found.
2. Sorry for the graphiql part, I did not know it's called that.