update nginx.example.conf for latest rich text CSP

docs/example.nginx.conf

@@ -102,7 +102,6 @@ server {
     set $unsafe 0;
     # the following assets are loaded via the sandbox domain
     # they unfortunately still require exceptions to the sandboxing to work correctly.
-    if ($uri = "/pad/inner.html") { set $unsafe 1; }
     if ($uri = "/sheet/inner.html") { set $unsafe 1; }
     if ($uri ~ ^\/common\/onlyoffice\/.*\/index\.html.*$) { set $unsafe 1; }