Remove duplicate message

locales/en/messages.json

@@ -1900,10 +1900,6 @@
         "message": "D Max increases D during quicker gyro and/or stick movements.<br><br>The 'Gain' factor increases D when the aircraft turns quickly or is shaking in propwash. Usually only 'Gain' is needed. <br><br>The 'Advance' factor increases D towards D Max during stick inputs. Usually it is not needed and should be set to zero.  Advance can be useful for low authority aircraft that tend to overshoot heavily.<br><br>Higher Gain values (eg 40) may be more suitable for freestyle by lifting D more readily.<br><br>WARNING: One of Gain or Advance must be set above about 20 or D will not increase as it should. Setting both to zero will lock D at the base value.",
         "description": "D Max feature helpicon message"
     },
-    "pidTuningDerivativeHelp": {
-        "message": "Baseline damping of ANY motion of the aircraft. <br /><br />Opposes movement whether caused by stick inputs or external influences (e.g. prop-wash or wind gusts)<br /><br />Higher D gains provide more stability and reduce overshoot.<br /><br />D amplifies noise (magnifies by 10x to 100x).  This can burn out motors if gains are too high or D isn't filtered well.<br /><br />D-term is a bit like the shock absorber on your car.",
-        "description": "Derivative helpicon message on PID table titlebar"
-    },
     "pidTuningPidSettings": {
         "message": "PID Controller Settings"
     },