[model loading] remove pointless log entries
This PR removes 2 IMO-pointless log entries that literally say "all is well". 

Log entries are useful for debugging problems, but just add to the noise that make more difficult to see useful entries, when they state the obvious, no?

@sgugger, @LysandreJik 


@LysandreJik, I can totally see your point.

But this one says the same thing twice:
```
            f"All model checkpoint weights were used when initializing {model.__class__.__name__}.\n"
            f"All the weights of {model.__class__.__name__} were initialized from the model checkpoint at {pretrained_model_name_or_path}.\n"
```

They aren't exactly the same but they say twice that there was no problem in loading the model

So as with your excellent example the following would be fitting:
```
"Loading model {name} at {path}"
(any exceptions go here)
"Model loaded"
```

Would you be open if changed this PR to follow this strategy?<|||||>They don't really say the same thing, I would see the first one as:

```
Checking if all checkpoints weights were used in the model ...
All checkpoint weights were used.
[...]
Checking if all weights of the model were initialized by the checkpoint ...
All model weights are initialized.
```
I think both serve a purpose:
1. Is the checkpoint meant for that architecture, or was it trained for another one.
2. Is the model perfectly initialized from that checkpoint, or will it require some fine-tuning.<|||||>The full current log for point 2 is:
``` 
               logger.info(
                    f"All the weights of {model.__class__.__name__} were initialized from the model checkpoint at {pretrained_model_name_or_path}.\n"
                    f"If your task is similar to the task the model of the checkpoint was trained on, "
                    f"you can already use {model.__class__.__name__} for predictions without further training."
                )
```

So that log's line 2+3 are still there. I didn't suggest to remove those.

But I feel that this is bordering on splitting hairs (from my side), so I will just let it be. 

Your explanation of its purpose makes sense, @LysandreJik. I'd have just tuned it up to make it more factual and less verbose ...

My issue is that I read those logs and not all of them feel like very readable to me...


