tweak error message in cal update script

scripts/cal_update_restart

@@ -40,7 +40,7 @@ return_code=$(curl \
 		  https://ldas-jobs.ligo-${site}.caltech.edu/~cal/archive/${IFO}/reports/latest/${filter_file}
 	   )
 if [[ "$return_code" != 200 ]] ; then
-    echo "filter download did not return 200 status: $return_code"
+    echo "ERROR: filter download did not return 200 status: $return_code"
     exit 1
 fi
 sha256sum ${filter_file}