fix: Fix typo in var name. (jitsi#1690)

Author: bgrozev

jicofo/rootfs/defaults/jicofo.conf

@@ -145,7 +145,7 @@ jicofo {
       {{ end }}
 
       {{ if .Env.JICOFO_CONF_SOURCE_SIGNALING_DELAYS }}
-      source-signaling-delays = {{ .Env.JICOFO_SOURCE_SIGNALING_DELAYS }}
+      source-signaling-delays = {{ .Env.JICOFO_CONF_SOURCE_SIGNALING_DELAYS }}
       {{ end }}
 
       {{ if .Env.JICOFO_CONF_MAX_AUDIO_SENDERS }}