Fix doctests for `DeiT` and `TFGroupViT`
# What does this PR do?

For `DeiT`: The parameter initialization is changed for some models in #19341. This can affect some tests where a checkpoint without head is used (so randomly initialized head). cc @alaradirik 

For `TFGroupViT`: We loved PyTorch too much (or not enough?) and want to use it in TensorFlow --> It's still too early :-)
_The documentation is not available anymore as the PR was closed or merged._