Removing prototype related things from release/0.14 branch (#6687)

* Remove test related to prototype

* Remove torchvision/prototype dir

* Remove references/depth/stereo because it depend on prototype

* Remove prototype related entries on mypy.ini

* Remove things related to prototype in pytest.ini

* clean setup.py from prototype

* Clean CI from prototype

* Remove unused expect file

torchvision/prototype/__init__.py

-from . import datasets, features, models, transforms, utils

torchvision/prototype/datasets/__init__.py

-try:
-    import torchdata
-except ModuleNotFoundError:
-    raise ModuleNotFoundError(
-        "`torchvision.prototype.datasets` depends on PyTorch's `torchdata` (https://github.com/pytorch/data). "
-        "You can install it with `pip install --pre torchdata --extra-index-url https://download.pytorch.org/whl/nightly/cpu"
-    ) from None
-
-from . import utils
-from ._home import home
-
-# Load this last, since some parts depend on the above being loaded first
-from ._api import list_datasets, info, load, register_info, register_dataset  # usort: skip
-from ._folder import from_data_folder, from_image_folder
-from ._builtin import *