add str hub token to repository when provided else fallback to default
# What does this PR do?

This PR fixes the Repository creation when using `PushToHubCallback`. Currently, the Repository is created assuming the `HF_TOKEN` is available on the machine, but that's not the case for every scenario. 
These changes check if the `hub_token` parameter is provided if yes then it is passed into the `Repository` if not the default value `True` is used. 

should we/can we add in the upcoming release to have it "fixed" for now and then improve on it? @Rocketknight1 @LysandreJik ? <|||||>Yes, agreed that it should be in the PR; pinging @Rocketknight1 for a quick review and will merge afterwards.<|||||>Also I'll be doing significant updates to the PushToHubCallback in the model card PR that's due Soon™, so I'll play around with it a bit more when I'm testing that.