Do not overwrite X-Forwarded-For when reverse-proxying to Synapse

We have a flow like this:
1. matrix.DOMAIN vhost (matrix-domain.conf)
2. matrix-synapse vhost (matrix-synapse.conf); or matrix-corporal container, if enabled
3. (optional) matrix-synapse vhost (matrix-synapse.conf), if matrix-corporal enabled
4. matrix-synapse container

We are setting `X-Forwarded-For` correctly in step #1, but were
overwriting it in step #2 with something inaccurate.

Not doing anything in step #2 is better than doing the wrong thing.
It's probably best if we append another reverse-proxy address there
though, although what we're doing now (with this patch) seems to yield
the correct result (when matrix-corporal is not enabled).

When matrix-corporal is enabled, we still seem to do the wrong thing for
some reason. It's something to be fixed later on.

roles/matrix-nginx-proxy/templates/nginx/conf.d/matrix-synapse.conf.j2

@@ -79,7 +79,6 @@ server {
 			location ~ {{ location }} {
 				proxy_pass http://generic_worker_upstream$request_uri;
 				proxy_set_header Host $host;
-				proxy_set_header X-Forwarded-For $remote_addr;
 			}
 			{% endfor %}
 		{% endif %}
@@ -90,7 +89,6 @@ server {
 			location ~ {{ location }} {
 				proxy_pass http://media_repository_upstream$request_uri;
 				proxy_set_header Host $host;
-				proxy_set_header X-Forwarded-For $remote_addr;
 
 				client_body_buffer_size 25M;
 				client_max_body_size {{ matrix_nginx_proxy_proxy_matrix_client_api_client_max_body_size_mb }}M;
@@ -106,7 +104,6 @@ server {
 			location ~ {{ location }} {
 				proxy_pass http://user_dir_upstream$request_uri;
 				proxy_set_header Host $host;
-				proxy_set_header X-Forwarded-For $remote_addr;
 			}
 			{% endfor %}
 		{% endif %}
@@ -117,7 +114,6 @@ server {
 			location ~ {{ location }} {
 				proxy_pass http://frontend_proxy_upstream$request_uri;
 				proxy_set_header Host $host;
-				proxy_set_header X-Forwarded-For $remote_addr;
 			}
 			{% endfor %}
 			{% if matrix_nginx_proxy_synapse_presence_disabled %}
@@ -125,7 +121,6 @@ server {
 			location ~ ^/_matrix/client/(api/v1|r0|unstable)/presence/[^/]+/status {
 				proxy_pass http://frontend_proxy_upstream$request_uri;
 				proxy_set_header Host $host;
-				proxy_set_header X-Forwarded-For $remote_addr;
 			}
 			{% endif %}
 		{% endif %}
@@ -150,7 +145,6 @@ server {
 		{% endif %}
 
 		proxy_set_header Host $host;
-		proxy_set_header X-Forwarded-For $remote_addr;
 
 		{% if matrix_nginx_proxy_proxy_synapse_metrics_basic_auth_enabled %}
 			auth_basic "protected";
@@ -172,7 +166,6 @@ server {
 		{% endif %}
 
 		proxy_set_header Host $host;
-		proxy_set_header X-Forwarded-For $remote_addr;
 
 		client_body_buffer_size 25M;
 		client_max_body_size {{ matrix_nginx_proxy_proxy_matrix_client_api_client_max_body_size_mb }}M;
@@ -199,7 +192,6 @@ server {
 			location ~ {{ location }} {
 				proxy_pass http://generic_worker_upstream$request_uri;
 				proxy_set_header Host $host;
-				proxy_set_header X-Forwarded-For $remote_addr;
 			}
 			{% endfor %}
 		{% endif %}
@@ -209,7 +201,6 @@ server {
 			location ~ {{ location }} {
 				proxy_pass http://media_repository_upstream$request_uri;
 				proxy_set_header Host $host;
-				proxy_set_header X-Forwarded-For $remote_addr;
 
 				client_body_buffer_size 25M;
 				client_max_body_size {{ matrix_nginx_proxy_proxy_matrix_federation_api_client_max_body_size_mb }}M;
@@ -231,7 +222,6 @@ server {
 		{% endif %}
 
 		proxy_set_header Host $host;
-		proxy_set_header X-Forwarded-For $remote_addr;
 
 		client_body_buffer_size 25M;
 		client_max_body_size {{ matrix_nginx_proxy_proxy_matrix_federation_api_client_max_body_size_mb }}M;