fixed the typo error in code

app.py

@@ -187,7 +187,7 @@ if len(ALL_FILES) > 0:
     with st.spinner(
             "🧠    Performing indexing of uplaoded documents... \n "
         ):
-        for i range(0, len(docs), batch_size):
+        for i in range(0, len(docs), batch_size):
             # find end of batch
             i_end = min(i+batch_size, len(docs))
             # extract batch