Revert "Collabora Online and Nextcloud, another try."

This reverts commit a4960969.

I think this breaks other stuff (like mail).

conf.d/nextcloud.shore.co.il.conf

@@ -21,9 +21,6 @@ server {
     include     snippets/ssl.conf;
     include     snippets/nextcloud-well-known.conf;
 
-    # Allow to include iframes in code.shore.co.il.
-    add_header  Content-Security-Policy "frame-ancestors https://code.shore.co.il";
-
     location / {
         proxy_pass              http://$nextcloud$request_uri;
         proxy_http_version      1.1;