Simplify partial() rough equivalent code (pythongh-124941)

Author: rhettinger

Doc/library/functools.rst

@@ -347,8 +347,7 @@ The :mod:`functools` module defines the following functions:
 
       def partial(func, /, *args, **keywords):
           def newfunc(*more_args, **more_keywords):
-              keywords_union = {**keywords, **more_keywords}
-              return func(*args, *more_args, **keywords_union)
+              return func(*args, *more_args, **(keywords | more_keywords))
           newfunc.func = func
           newfunc.args = args
           newfunc.keywords = keywords