fix: remove invalid V12 target

Removed entry for HelloRadioSky V12 from the firmware list.

Author: pfeerick

fw.json

@@ -16,7 +16,6 @@
         ["FrSky X9D Plus 2019", "x9dp2019-"],
         ["FrSky X9E", "x9e-"],
         ["FrSky X9E Hall", "x9e-hall-"],
-        ["HelloRadioSky V12", "v12-"],
         ["HelloRadioSky V14", "v14-"],
         ["HelloRadioSky V16", "v16-"],
         ["iFlight Commando 8", "commando8-"],