__jitsi_meet: improve screensharing in certain situations

We had been noticing issues when sharing screen that required
refreshing (sometimes from presentors, sometimes from receivers), or
else people would get a shared black screen or hanging screen after
some time.

This somewhat undocumented jitsi-videobridge setting appears to have
fixed the issue on all instances tested:

    videobridge.cc.trust-bwe = false

Announcement: https://agora.exo.cat/t/exofasia-3/276#meetexocatguifinet-4

Relevant links:
- https://community.jitsi.org/t/jitsi-users-video-turned-off-to-save-bandwidth-on-meet-jit-si/12735/2
- https://github.com/jitsi/jitsi-videobridge/blob/master/CONFIG.md#migrating-from-old-config

Sponsored by:	camilion.eu, eXO.cat

type/__jitsi_meet/manifest

@@ -254,6 +254,9 @@ videobridge {
             enabled = true
         }
     }
+    cc {
+        trust-bwe = false
+    }
 }
 EOFJVB