Iterate through filtered file types instead of all listed files (#6258)

# Iterate through filtered file types instead of all listed files

Fixes #6257

#4926 originally added the
functionality to filter by file type, storing the filtered files in
`_files`

#5220 removed the
functionality when adding code to filter trashed files by using the
`files` variables instead of the `_files` variable.

This PR simply adds the functionality back by using `_files` again.

#### Who can review?

@hwchase17 - project lead
@eyurtsev

langchain/document_loaders/googledrive.py

@@ -228,7 +228,7 @@ def _load_documents_from_folder(
             _files = files
 
         returns = []
-        for file in files:
+        for file in _files:
             if file["trashed"] and not self.load_trashed_files:
                 continue
             elif file["mimeType"] == "application/vnd.google-apps.document":