Feature/update readme

[Taniya-Das]

remove outdated information

[josvandervelde]

This is quite a minimal change :)
Did you forget to commit some files?

I'd suggest removing more information, such "Starting a MySQL Server" (maybe keep a part to say how to connect to the db, mentioning ./scripts/database-connect.sql should be enough, I think), "#### Persistent Storage", "### Starting the REST API", "#### Using the Docker container". "#### Editing Files Locally".

Please also delete
"Please ask Jos van der Velde ([email protected]) for the keycloak secret, and to give your user the correct roles."

[josvandervelde]

Thanks!

I saw that the Authentication part is not yet up to date, can you change that as well?
"Currently, the code is on default coupled with a keycloak running on test.openml.org." <-- by default we're using the local Keycloak now.