uwsgi: Increase buffer-size to 8192.

For users putting Zulip behind certain proxies (and potentially some
third-party API clients), buffer sizes can exceed the uwsgi default of
4096.  Since we aren't doing such high-throughput APIs that a small
buffer size is valuable, we should just raise this for everyone.

puppet/zulip/templates/uwsgi.ini.template.erb

@@ -7,6 +7,7 @@ chmod-socket=700
 chown-socket=zulip:zulip
 processes=<%= @uwsgi_processes %>
 harakiri=20
+buffer-size=8192
 post-buffering=4096
 env= LANG=en_US.UTF-8
 uid=zulip