[rbmaradio] add 192k bitrate

[jnsl]

While older content is still available in 256, 128 and 96k, currently redbull radio serves MP3s in 128 and 192k.

youtube-dl -g -v https://www.redbullradio.com/shows/peak-time/episodes/may-29-2018
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['-g', '-v', 'https://www.redbullradio.com/shows/peak-time/episodes/may-29-2018']
[debug] Encodings: locale cp1252, fs mbcs, out cp437, pref cp1252
[debug] youtube-dl version 2018.06.02
[debug] Python version 3.4.4 (CPython) - Windows-10-10.0.17682
[debug] exe versions: ffmpeg 4.0, ffprobe 4.0, rtmpdump 2.3
[debug] Proxy map: {}
[debug] Default format spec: bestvideo+bestaudio/best
https://audio.rbmaradio.com/PT_21288_Peak_Time_Live__Errorsmith__DJ_Stingray_and_Volvox_RW_2H.mp3?cbr=128

cf. https://audio.rbmaradio.com/PT_21288_Peak_Time_Live__Errorsmith__DJ_Stingray_and_Volvox_RW_2H.mp3?cbr=192