fix: remove file modify check for auto retriever

[Wendong-Fan]

Description

we used the meta data from unstructured io Element to check whether the file with same name has been modified, but this property has been removed in unstructured io v0.14.0 we are currently using, which makes the file modify check feature not available, so I remove this check temporarily before we find other way to do file modify check

Motivation and Context

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Implemented Tasks

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