Remove --max-gain CLI option from docs

The option didn't make sense as max-gain is the default state, so it's
already on unless you use the --gain option.

README.md

@@ -82,7 +82,6 @@ The following options are available when running `airplanejs`:
 - `--device <index>` - Select RTL dongle (alias: `-d`, default: `0`)
 - `--frequency <hz>` - Set custom frequency (alias: `-f`, default: `1090000000`)
 - `--gain <gain>` - Set custom tuner gain (alias: `-g`)
-- `--max-gain` - Set tuner gain to highest possible value (default: on)
 - `--auto-gain` - Disable manual tuner gain (default: off)
 - `--enable-agc` - Use Automatic Gain Control (default: off)
 - `--port <port>` - Set custom HTTP server port (alias: `-p`, default: `3000`)

server.js

@@ -204,7 +204,6 @@ function help () {
  console.log(' --device -d <index> Select RTL dongle (default: 0)')
  console.log(' --frequency -f <hz> Set custom frequency (default: 1090000000)')
  console.log(' --gain -g <gain> Set custom tuner gain')
- console.log(' --max-gain Set tuner gain to highest possible value (default: on)')
  console.log(' --auto-gain Disable manual tuner gain (default: off)')
  console.log(' --enable-agc Use Automatic Gain Control (default: off)')
  console.log(' --port -p <port> Set custom HTTP server port (default: 3000)')