Fix nginx: remove redundant text/html from sub_filter_types (STI-102)

nginx includes text/html by default for sub_filter — adding it explicitly
causes a duplicate MIME type warning on reload.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

deploy-production/nginx.conf

@@ -99,7 +99,7 @@ server {
         proxy_set_header Accept-Encoding "";
 
         # Apply sub_filter to HTML, JS, and CSS responses
-        sub_filter_types text/html application/javascript text/css;
+        sub_filter_types application/javascript text/css;
         sub_filter_once off;
 
         # HTML: set <base href> so the SPA router knows its prefix