[doc] post-conversion: incosistent "default to"
After the conversion we ended up with inconsistent values for `defaults to` - sometimes it's `formatted`, other times it's *italics*, with former being the prevailing form. Example:
```
src/transformers/generation_tf_utils.py:            use_cache: (`bool`, *optional*, defaults to `True`):
src/transformers/generation_tf_utils.py:            output_attentions (`bool`, *optional*, defaults to *False*):
```
but there is a lot more of these

@sgugger 
It's not the conversion fault, those were inconsistent before. Meaning some were properly set with an :obj: marker or double backticks while other had simple backticks and were thus converted in italics.

By all means, if you want to do a batch conversion, the proper format is \`False\` (or \`True\`)<|||||>Will do,

Also while fixing this I see there are still quite a few `:obj:` leftovers - is it still a WIP?

```
grep -Ir :obj: src
src/transformers/models/t5/modeling_t5.py:            assert self.is_decoder, f":obj:`use_cache` can only be set to `True` if {self} is used as a decoder"
src/transformers/models/tapas/modeling_tapas.py:        input_mask_float (:obj: *torch.FloatTensor* of shape `(batch_size, seq
[...]
```<|||||>No. The first example is not a docstring, so not touched by the conversion scripts. The second one seemed to have a space between the :obj: and the \` so was not properly converted (the torch.FloatTensor is not supposed to be in italics).

You should wait a tiny bit more before doing any conversion as I'm in the process of changing lots of docstrings in #14950 (will merge it when it's green).<|||||>That was just a small snippet, the full match is 44 lines. should be easy to reproduce.

Please take your time, I was just flagging these in case it was missed.<|||||>OK PR is merged!
If you want to hunt down all the remaining :obj:/:class:/:meth:/:func: that would be amazing (and leave me more time to work on #14032 this week :-) )<|||||>Sure, once you approve https://github.com/huggingface/transformers/pull/14951 and it is merged to avoid conflicts.<|||||>Done. I think there might also be some incomplete :obj or obj: in the wild (saw one on #14951).<|||||>So what of all these `:obj:` that are not in the doc string - do we simply remove those?

e.g.:

```
src/transformers/models/t5/modeling_t5.py:            assert self.is_decoder, f":obj:`use_cache` can only be set to `True` if {self} is used as a decoder"
examples/research_projects/quantization-qdqbert/utils_qa.py:        prefix (:obj:`str`, `optional`):
examples/research_projects/deebert/src/modeling_highway_roberta.py:            loss (:obj:`torch.FloatTensor` of shape :obj:`(1,)`, `optional`, returned when :obj:`label` is provided):
```

<|||||>Yes, we use Markdown style everywhere. Would just not touch the research projects. as I haven't converted the docstrings there.