autodata could not create document for instance variables with type annotation

[tk0miya]

Describe the bug
autodata could not create document for instance variables with type annotation.

To Reproduce

# example.py
var: int

# index.rst
.. autodata:: example.var

It causes AttributeError

WARNING: autodoc: failed to import data 'var' from module 'example'; the following exception was raised:
Traceback (most recent call last):
  File "/Users/tkomiya/work/sphinx/sphinx/util/inspect.py", line 343, in safe_getattr
    return getattr(obj, name, *defargs)
AttributeError: module 'example' has no attribute 'var'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/tkomiya/work/sphinx/sphinx/ext/autodoc/importer.py", line 106, in import_object
    obj = attrgetter(obj, mangled_name)
  File "/Users/tkomiya/work/sphinx/sphinx/ext/autodoc/__init__.py", line 316, in get_attr
    return autodoc_attrgetter(self.env.app, obj, name, *defargs)
  File "/Users/tkomiya/work/sphinx/sphinx/ext/autodoc/__init__.py", line 2269, in autodoc_attrgetter
    return safe_getattr(obj, name, *defargs)
  File "/Users/tkomiya/work/sphinx/sphinx/util/inspect.py", line 359, in safe_getattr
    raise AttributeError(name) from exc
AttributeError: var

Expected behavior
Document should be generated successfully like when I used automodule.

Your project
N/A

Screenshots
N/A

Environment info

• OS: Mac
• Python version: 3.9.0
• Sphinx version: HEAD of 3.x
• Sphinx extensions: sphinx.ext.autodoc
• Extra tools: Nothing

Additional context
Nothing