Don't call download_multipart for 1 chunk

Previously, where a file was larger than `$LARGE_FILE_SIZE` but smaller
than `$CHUNK_SIZE*2`, `download_multipart` would be called but would
only download one (1) chunk that was the whole file.

This fix keeps the same download performance as before but optimizes
processing chunks out.

src/libpostal_data

@@ -36,10 +36,11 @@ export LC_ALL=C
 EPOCH_DATE="Jan  1 00:00:00 1970"
 
 MB=$((1024*1024))
-LARGE_FILE_SIZE=$((100*$MB))
-
 CHUNK_SIZE=$((64*$MB))
 
+LARGE_FILE_SIZE=$((CHUNK_SIZE*2))
+
+
 NUM_WORKERS=10
 
 function kill_background_processes {