Add 2HR option to list (openaps#1171)

Just a very minor update to reflect latest version of Nightscout with support for 2HR option

Author: hartvig

docs/docs/While You Wait For Gear/nightscout-setup.md

@@ -368,7 +368,7 @@ Nightscout, however, has its own COB pill, which decays carbs *statically*, and
 
 ### How to display OpenAPS purple prediction/forecast lines
 
-* Click the three dots next to your timeframe horizon (3HR, 6HR, 12HR, 24HR) and then enable “Show OpenAPS Forecasts”. Don't see this option? Check and make sure you added this variable and that your OpenAPS has successfully run.
+* Click the three dots next to your timeframe horizon (2HR, 3HR, 6HR, 12HR, 24HR) and then enable “Show OpenAPS Forecasts”. Don't see this option? Check and make sure you added this variable and that your OpenAPS has successfully run.
 
 ### Understanding the OpenAPS pill