treat html extension as an implementation detail

These redirects aren't being used for any of the actual pages based on
the access logs.

nginx/nginx.conf

@@ -133,10 +133,6 @@ http {
         gzip_static on;
         brotli_static on;
 
-        if ($request_uri ~ ^/(.*)\.html$) {
-            return 301 /$1;
-        }
-
         if ($request_uri ~ (.*)//(.*)) {
             return 301 $1/$2;
         }
@@ -293,7 +289,7 @@ http {
             add_header Cache-Control "public, max-age=1800";
         }
 
-        location ~ "\.(br|gz)$" {
+        location ~ "\.(br|gz|html)$" {
             internal;
         }