fix unittest syntax

Author: nim65s

python/eigenpy/windows_dll_manager.py

@@ -1,6 +1,5 @@
 import contextlib
 import os
-import sys
 
 
 def get_dll_paths():
@@ -59,7 +58,4 @@ def __exit__(self, *exc_details):
 
 
 def build_directory_manager():
-    if sys.version_info >= (3, 8):
-        return DllDirectoryManager()
-    else:
-        return PathManager()
+    return DllDirectoryManager()