Fix infer shape error for paddle.add_n

[DanielSun11]

PR Category

Operator Mechanism

PR Types

Bug fixes

Description

修复 #73550 引起的bug。
具体bug报错：
http://yq01-qianmo-com-255-137-11.yq01.baidu.com/jelly_logs/20250705035016-39478cc0-606e-4e35-a60a-739bc095e217/logs/legacy_det/cases/solov2%5Esolov2_r101_vd_fpn_3x_coco_%E5%8D%95%E5%8D%A1%E5%8A%A8%E8%BD%AC%E9%9D%99%E8%AE%AD%E7%BB%83.log
影响到paddle Detection的训练用例。

pcard-67164

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

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Additional details and impacted files

@@             Coverage Diff             @@
##             develop    #73877   +/-   ##
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  Coverage           ?   100.00%           
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  Files              ?         2           
  Lines              ?         6           
  Branches           ?         0           
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  Hits               ?         6           
  Misses             ?         0           
  Partials           ?         0           

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