bpo-31047: Fix ntpath.abspath to trim ending separator (GH-10082)

Regression in b0bf51b32240369ccb736dc32ff82bb96f375402.
diff --git a/Lib/ntpath.py b/Lib/ntpath.py
index 0e6de28..11bb297 100644
--- a/Lib/ntpath.py
+++ b/Lib/ntpath.py
@@ -523,7 +523,7 @@
     def abspath(path):
         """Return the absolute version of a path."""
         try:
-            return _getfullpathname(path)
+            return normpath(_getfullpathname(path))
         except (OSError, ValueError):
             return _abspath_fallback(path)