isabelle-prepare: fix: use correct filename

ulo/isabelle-prepare.sh

@@ -25,6 +25,6 @@ for file in $files; do
 
     # uncompress, fix iris, compress again
     unxz "$file"
-    sed -i 's/|/%7C/g' "$file"
+    sed -i 's/|/%7C/g' "$rdf_file"
     gzip "$rdf_file"
 done