fix python 3.10 loading issue after bb8e84e

The error is below.

It was failing because Callable was checking if `ifcopenshell.entity_instance` is a callable and at runtime actually it's not, it's a module.
In python 3.11 they've removed that check and therefore it's not throwing an error. Enabling forward annotations fixes it for python 3.10.
Not sure if there is a need to ensure `ifcopenshell.entity_instance` should be recgonized by python as a class at runtime rather than a module since we need it just for type checking and type checking seems to be clever enough to prioritize module classes over submodules.

  File "C:\Users\user_name\AppData\Roaming\Blender Foundation\Blender\4.0\scripts\addons\blenderbim\bim\__init__.py", line 25, in <module>
    from . import handler, ui, prop, operator, helper
  File "C:\Users\user_name\AppData\Roaming\Blender Foundation\Blender\4.0\scripts\addons\blenderbim\bim\handler.py", line 23, in <module>
    import ifcopenshell.api.owner.settings
  File "C:\Users\user_name\AppData\Roaming\Blender Foundation\Blender\4.0\scripts\addons\blenderbim\libs\site\packages\ifcopenshell\__init__.py", line 85, in <module>
    from .file import file
  File "C:\Users\user_name\AppData\Roaming\Blender Foundation\Blender\4.0\scripts\addons\blenderbim\libs\site\packages\ifcopenshell\file.py", line 179, in <module>
    class file:
  File "C:\Users\user_name\AppData\Roaming\Blender Foundation\Blender\4.0\scripts\addons\blenderbim\libs\site\packages\ifcopenshell\file.py", line 382, in file
    def __getattr__(self, attr) -> Union[Any, Callable[..., ifcopenshell.entity_instance]]:
  File "C:\Program Files\Blender Foundation\Blender 4.0\4.0\python\lib\typing.py", line 1206, in __getitem__
    return self.__getitem_inner__(params)
  File "C:\Program Files\Blender Foundation\Blender 4.0\4.0\python\lib\typing.py", line 312, in inner
    return func(*args, **kwds)
  File "C:\Program Files\Blender Foundation\Blender 4.0\4.0\python\lib\typing.py", line 1212, in __getitem_inner__
    result = _type_check(result, msg)
  File "C:\Program Files\Blender Foundation\Blender 4.0\4.0\python\lib\typing.py", line 176, in _type_check
    raise TypeError(f"{msg} Got {arg!r:.100}.")
TypeError: Callable[args, result]: result must be a type. Got <module 'ifcopenshell.entity_instance' from 'C:\\Users\\user_name\\AppData\\Roaming\\Blender F.

src/ifcopenshell-python/ifcopenshell/file.py

@@ -16,7 +16,7 @@
 # You should have received a copy of the GNU Lesser General Public License
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
-
+from __future__ import annotations
 import os
 import re
 import numbers