Remove type annotations from signatures in html docs (pytorch#49294)

Summary:
One unintended side effect of moving type annotations inline was that those annotations now show up in signatures in the html docs. This is more confusing and ugly than it is helpful. An example for `MaxPool1d`:

![image](https://user-images.githubusercontent.com/98330/102010280-77f86900-3d3d-11eb-8f83-e7ee0991ed92.png)

This makes the docs readable again. The parameter descriptions often already have type information, and there will be many cases where the type annotations will make little sense to the user (e.g., returning typevar T, long unions).

Change to `MaxPool1d` example:

![image](https://user-images.githubusercontent.com/98330/102010304-91011a00-3d3d-11eb-860d-ffa174b4d43b.png)

Note that once we can build the docs with Sphinx 3 (which is far off right now), we have two options to make better use of the extra type info in the annotations (some of which is useful):
- `autodoc_type_aliases`, so we can leave things like large unions unevaluated to keep things readable
- `autodoc_typehints = 'description'`, which moves the annotations into the parameter descriptions.

Another, more labour-intensive option, is what vadimkantorov suggested in pytorchgh-44964: show annotations on hover. Could also be done with some foldout, or other optional way to make things visible. Would be nice, but requires a Sphinx contribution or plugin first.

Pull Request resolved: pytorch#49294

Reviewed By: glaringlee

Differential Revision: D25535272

Pulled By: ezyang

fbshipit-source-id: 5017abfea941a7ae8c4595a0d2bdf8ae8965f0c4

docs/source/conf.py

@@ -161,7 +161,7 @@
 # TODO: verify this works as expected
 release = 'master'
 
-# Customized html_title here. 
+# Customized html_title here.
 # Default is " ".join(project, release, "documentation") if not set
 if RELEASE:
     # remove hash (start with 'a') from version number if any
@@ -192,6 +192,9 @@
 # Disable docstring inheritance
 autodoc_inherit_docstrings = False
 
+# Disable displaying type annotations, these can be very verbose
+autodoc_typehints = 'none'
+
 
 # -- katex javascript in header
 #
@@ -253,9 +256,9 @@ def setup(app):
         add_css(css_file)
 
 # From PyTorch 1.5, we now use autogenerated files to document classes and
-# functions. This breaks older references since 
+# functions. This breaks older references since
 # https://docs.pytorch.org/torch.html#torch.flip
-# moved to 
+# moved to
 # https://docs.pytorch.org/torch/generated/torchflip.html
 # which breaks older links from blog posts, stack overflow answers and more.
 # To mitigate that, we add an id="torch.flip" in an appropriated place
@@ -278,7 +281,7 @@ def visit_reference(self, node):
                 # to autogenerated content
                 anchor = ref_anchor[1]
                 txt = node.parent.astext()
-                if txt == anchor or txt == anchor.split('.')[-1]: 
+                if txt == anchor or txt == anchor.split('.')[-1]:
                     self.body.append('<p id="{}"/>'.format(ref_anchor[1]))
         return old_call(self, node)
     Klass.visit_reference = visit_reference