remove nginx-secure-token-module from the nginx build

Kaltura deleted the nginx-secure-token-module repo, so the tarball download in build_nginx.sh returned a 404 and any build without a cached nginx layer failed. This drops the module and its secure_token directives from the vod location.

docker/main/rootfs/usr/local/nginx/conf/nginx.conf

@@ -143,9 +143,6 @@ http {
             # version 6 (RFC 8216 section 7); the module default is 4
             vod_hls_version 6;
 
-            secure_token $args;
-            secure_token_types application/vnd.apple.mpegurl;
-
             include security_headers.conf;
             add_header Cache-Control "no-store";
             expires off;