support passing encode argument for RequestSetLiveStreamMode

[TinfoilSubmarine]

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Description

This enables passing --encode | --no-encode to livestream.py, defaulting (as before) to True:

$ python3 livestream.py -h                                                             main 
usage: livestream.py [-h] [--min_bit MIN_BIT] [--max_bit MAX_BIT] [--start_bit START_BIT] [--resolution {4,7,12}]
                     [--fov {0,4,3}] [--encode | --no-encode] [--log LOG] [--identifier IDENTIFIER]
                     ssid password url

Connect to the GoPro via BLE only, configure then start a Livestream, then display it with CV2.

positional arguments:
  ssid                  WiFi SSID to connect to.
  password              Password of WiFi SSID.
  url                   RTMP server URL to stream to.

options:
  -h, --help            show this help message and exit
  --min_bit MIN_BIT     Minimum bitrate.
  --max_bit MAX_BIT     Maximum bitrate.
  --start_bit START_BIT
                        Starting bitrate.
  --resolution {4,7,12}
                        Resolution.
  --fov {0,4,3}         Field of View.
  --encode, --no-encode
                        Save video to sdcard.
  --log LOG             Location to store detailed log
  --identifier IDENTIFIER
                        Last 4 digits of GoPro serial number, which is the last 4 digits of the default camera SSID.
                        If not used, first discovered GoPro will be connected to
                        ```