Add Note for Place of Executor in Parallel Environment (#39063)

Add note for Place of Executor in parallel environment

python/paddle/fluid/executor.py

@@ -622,7 +622,9 @@ class Executor(object):
             is CPU version, the default device would be set to `CPUPlace()` . If Paddle is
             GPU version, the default device would be set to `CUDAPlace(0)` . Default is None.
             If ``place`` is string, it can be ``cpu``, and ``gpu:x``, where ``x`` 
-            is the index of the GPUs.
+            is the index of the GPUs. Note: users only pass one Place or None to initialize
+            Executor when using multiple-cards. Other APIs will override the cards. See
+            `document for multiple-cards <https://www.paddlepaddle.org.cn/documentation/docs/en/develop/guides/01_paddle2.0_introduction/update_en.html#stand-alone-multi-card-launch>`_ 
 
     Returns:
         Executor