Fix type hints for old python versions

src/AlignMolecule/__init__.py

@@ -2,10 +2,8 @@
 # Align a molecule using Kabsch algorithm.
 # https://en.wikipedia.org/wiki/Kabsch_algorithm
 
-import platform
 
-if tuple(int(v) for v in platform.python_version_tuple()) <= (3, 8):
-    from __future__ import annotations  # noqa: F404
+from __future__ import annotations
 
 from ovito.data import DataCollection
 from ovito.modifiers import AffineTransformationModifier