config: fix opusMaxAverageBitrate option name

Must match the lib-jitsi-meet counterpart.

Fixes: https://github.com/jitsi/jitsi-meet/issues/7384

config.js

     // Sets the preferred target bitrate for the Opus audio codec by setting its
     // 'maxaveragebitrate' parameter. Currently not available in p2p mode.
     // Valid values are in the range 6000 to 510000
-    // opusMaxAvgBitrate: 20000,
+    // opusMaxAverageBitrate: 20000,
 
     // Video
 

react/features/base/config/configWhitelist.js

     'minParticipants',
     'nick',
     'openBridgeChannel',
-    'opusMaxAvgBitrate',
+    'opusMaxAverageBitrate',
     'p2p',
     'pcStatsInterval',
     'preferH264',