Use chmod a-w instead of -w

Some versions of chmod give warnings that not all permissions are
changed if you use `-w`, because bits that are set in the umask are not
affected.

Belonging to [master]:
  - OpenModelica/OpenModelica-testsuite#1009

openmodelica/interactive-API/Rename.mos

@@ -1,7 +1,7 @@
 // name:      Rename
 // keywords:  rename Component
 // status:    correct
-// setup_command: chmod -w RenameRO.mo
+// setup_command: chmod a-w RenameRO.mo
 //
 loadFile("Rename.mo"); getErrorString();