use lower() to match upper file extension name (#2069)

Author: BetterAndBetterII

app/backend/prepdocslib/filestrategy.py

@@ -17,7 +17,7 @@ async def parse_file(
     category: Optional[str] = None,
     image_embeddings: Optional[ImageEmbeddings] = None,
 ) -> List[Section]:
-    key = file.file_extension()
+    key = file.file_extension().lower()
     processor = file_processors.get(key)
     if processor is None:
         logger.info("Skipping '%s', no parser found.", file.filename())