stop documenting EFxx

it doesn't even work on linear pitch

papers/doc/3-pattern/effects.md

@@ -57,9 +57,6 @@ however, effects are continuous, which means you only need to type it once and t
 - `EDxx`: delay note by `xx` ticks.
 - `EExx`: send external command.
   - this effect is currently incomplete.
-- `EFxx`: add or subtract global pitch.
-  - this effect is rather weird. use with caution.
-  - `80` is center.
 - `F0xx`: change song Hz by BPM value.
 - `F1xx`: single tick slide up.
 - `F2xx`: single tick slide down.

src/engine/engine.cpp

@@ -110,8 +110,6 @@ const char* DivEngine::getEffectDesc(unsigned char effect, int chan, bool notNul
       return "EDxx: Note delay";
     case 0xee:
       return "EExx: Send external command";
-    case 0xef:
-      return "EFxx: Set global tuning (quirky!)";
     case 0xf0:
       return "F0xx: Set tick rate (bpm)";
     case 0xf1: