Documentation for VOICE_BRIDGE_LEN default doesn't match actual default value

[kepstin]

In the scalelite documentation the default value for VOICE_BRIDGE_LEN is listed as 7. However, in the code, the actual default value is 9.

Either the documentation has to be updated to match the code, or the code needs to be updated to match the documentation. Either way, we need to ensure that the default value is compatible with the unmodified freeswitch configuration on all supported BigBlueButton versions.