Update RealSense version error handling

[m3d]

No description provided.

[m3d]

>>> from pyrealsense2 import pyrealsense2 as rs
>>> rs.__version__
'2.47.0'
>>> c = rs.context()
>>> exit()

works as well as

>>> import pyrealsense2 as rs
>>> rs.__version__
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'pyrealsense2' has no attribute '__version__'
>>> rs.pyrealsense2.__version__
'2.47.0'
>>> c2 = rs.context()
>>> exit()

[m3d]

workaround with __init__.py works: IntelRealSense/librealsense#6820 (comment) ... closing.