[fix] update test for date function in data download script

src/libpostal_data

@@ -115,7 +115,7 @@ download_file() {
             curl $url --retry 3 --retry-delay 2 -o $local_path
         fi
 
-        if date -ur . >/dev/null 2>&1; then
+        if date -d "@$(date -ur . +%s)" >/dev/null 2>&1; then
             echo $(date -d "$(date -d "@$(date -ur $local_path +%s)") + 1 second") > $updated_path;
         elif stat -f %Sm . >/dev/null 2>&1; then
             echo $(date -r $(stat -f %m $local_path) -v+1S) > $updated_path;