debian: don't delete /var/log/nginx on package removal.

debian/nginx.postrm

diff --git a/debian/nginx.postrm b/debian/nginx.postrm
index 2755de9..252e00d 100644
--- a/debian/nginx.postrm
+++ b/debian/nginx.postrm
@@ -6,9 +6,6 @@
     purge)
         rm -rf /var/cache/nginx /var/log/nginx /etc/nginx
         ;;
-    remove)
-        rm -rf /var/cache/nginx /var/log/nginx
-        ;;
     remove|upgrade|failed-upgrade|abort-install|abort-upgrade|disappear)
         ;;
     *)