Revert "bpo-33929: multiprocessing: fix handle leak on race condition (GH-7921)" (GH-7963)

This reverts commit 8b1ebcd7cb3319273ea635df78ebf9ad40171514.
diff --git a/Lib/multiprocessing/reduction.py b/Lib/multiprocessing/reduction.py
index 473fd59..deca19c 100644
--- a/Lib/multiprocessing/reduction.py
+++ b/Lib/multiprocessing/reduction.py
@@ -68,16 +68,12 @@
     __all__ += ['DupHandle', 'duplicate', 'steal_handle']
     import _winapi
 
-    def duplicate(handle, target_process=None, inheritable=False,
-                  *, source_process=None):
+    def duplicate(handle, target_process=None, inheritable=False):
         '''Duplicate a handle.  (target_process is a handle not a pid!)'''
-        current_process = _winapi.GetCurrentProcess()
-        if source_process is None:
-            source_process = current_process
         if target_process is None:
-            target_process = current_process
+            target_process = _winapi.GetCurrentProcess()
         return _winapi.DuplicateHandle(
-            source_process, handle, target_process,
+            _winapi.GetCurrentProcess(), handle, target_process,
             0, inheritable, _winapi.DUPLICATE_SAME_ACCESS)
 
     def steal_handle(source_pid, handle):