Cleanup config attrs
# What does this PR do?

These are vision models, and they don't form encoder-decoder themselves (unlike some text models like `Bart`).

Furthermore, the current default value (specified in each config  class `__init__`) for these configs are `False`, which is the same as the default value in `PretrainedConfig`. So we can just remove it from the parameters, and rely on `**kwargs` in the call to `super.__init__` .

_The documentation is not available anymore as the PR was closed or merged._