!14238 Remove worng comment of laplace op

From: @pkuliuliu
Reviewed-by: @lilongfei15,@jxlang910,@zhunaipan
Signed-off-by: @zhunaipan

mindspore/ops/composite/random_ops.py

@@ -91,7 +91,7 @@ def laplace(shape, mean, lambda_param, seed=None):
         The dtype is float32.
 
     Supported Platforms:
-        ``Ascend`` ``GPU`` ``CPU``
+        ``Ascend``
 
     Examples:
         >>> from mindspore import Tensor