Fix builder config creation with data_dir
The data_dir parameter wasn't taken into account to create the config_id, therefore the resulting builder config was considered not custom. However a builder config that is non-custom must not have a name that collides with the predefined builder config names. Therefore it resulted in a `ValueError("Cannot name a custom BuilderConfig the same as an available...")`

I fixed that by commenting the line that used to ignore the data_dir when creating the config.

It was previously ignored before the introduction of config id because we didn't want to change the config name. Now it's fine to take it into account for the config id.

Now creating a config with a data_dir works again @patrickvonplaten 