Update rebuilderd-worker and enable diffoscope

rebuilderd-worker now supports an diffoscope output limit allowing us to
define how much data will be POST'ed to rebuilderd via nginx.

roles/rebuilderd/templates/nginx.d.conf.j2

@@ -51,7 +51,7 @@ server {
     }
 
     location /api/v0/build/report {
-	    client_max_body_size 128M;
+	    client_max_body_size 10M;
 	    proxy_pass http://127.0.0.1:8484;
     }
 }

roles/rebuilderd/templates/rebuilderd-worker.conf.j2

 endpoint = "https://reproducible.archlinux.org"
-#gen_diffoscope = true
 signup_secret = "{{ vault_rebuilderd_signup_secret }}"
+
+[diffoscope]
+enabled = true
+max_bytes = 10485760 # 10 MiB