Delete unused feather flag

data/json/monsters/bird.json

@@ -358,6 +358,6 @@
     "fear_triggers": [ "SOUND", "PLAYER_CLOSE", "FRIEND_ATTACKED", "FRIEND_DIED", "FIRE", "HURT" ],
     "death_function": [ "NORMAL" ],
     "biosignature": { "biosig_item": "feces_bird", "biosig_timer": 4 },
-    "flags": [ "SEES", "HEARS", "SMELLS", "ANIMAL", "PATH_AVOID_DANGER_1", "WARM", "FLIES", "FEATHER", "SWARMS", "BIRDFOOD" ]
+    "flags": [ "SEES", "HEARS", "SMELLS", "ANIMAL", "PATH_AVOID_DANGER_1", "WARM", "FLIES", "SWARMS", "BIRDFOOD" ]
   }
 ]

doc/JSON_FLAGS.md

@@ -940,7 +940,6 @@ Other monster flags.
 - ```ELECTRIC``` Shocks unarmed attackers.
 - ```ELECTRONIC``` e.g. A Robot; affected by emp blasts and other stuff.
 - ```FAT``` May produce fat when butchered.
-- ```FEATHER``` May produce feathers when butchered.
 - ```FILTHY``` Any clothing it drops will be filthy.  The squeamish trait prevents wearing clothing with this flag, one can't craft anything from filthy components, and wearing filthy clothes may result in infection if hit in melee.
 - ```FIREPROOF``` Immune to fire.
 - ```FIREY``` Burns stuff and is immune to fire.

src/monstergenerator.cpp

@@ -116,7 +116,6 @@ std::string enum_to_string<m_flag>( m_flag data )
         case MF_FUR: return "FUR";
         case MF_LEATHER: return "LEATHER";
         case MF_WOOL: return "WOOL";
-        case MF_FEATHER: return "FEATHER";
         case MF_CBM_CIV: return "CBM_CIV";
         case MF_BONES: return "BONES";
         case MF_FAT: return "FAT";

src/mtype.h

@@ -106,7 +106,6 @@ enum m_flag : int {
     MF_FUR,                 // May produce fur when butchered
     MF_LEATHER,             // May produce leather when butchered
     MF_WOOL,                // May produce wool when butchered
-    MF_FEATHER,             // May produce feather when butchered
     MF_BONES,               // May produce bones and sinews when butchered; if combined with POISON flag, tainted bones, if combined with HUMAN, human bones
     MF_FAT,                 // May produce fat when butchered; if combined with POISON flag, tainted fat
     MF_CONSOLE_DESPAWN,     // Despawns when a nearby console is properly hacked