Update postrm

add logic

debian/postrm

@@ -1,2 +1,6 @@
 #!/bin/bash
-rm -rf /usr/bin/up
+if [[ "$(file /usr/bin/up)" =~ "symbolic link to /usr/bin/update" ]]; then
+  rm -rf /usr/bin/up
+else
+  echo "It looks like your '/usr/bin/up' file isn't a symbolic link to '/usr/bin/update', so it hasn't been removed. If you stil want to remove it, you can do so with: sudo rm -f /usr/bin/up"
+fi