Unfortunately, there are several LiquidCrystal_I2C libraries. The one that uses POSITIVE is the "NewLiquidCrystal_lib" GitHub - fmalpartida/New-LiquidCrystal: Clone of the new liquid crystal library from: https://bitbucket.org/fmalpartida/new-liquidcrystal
You can also switch over to the hd44780 library and adjust your code accordingly