Fix spell damage bonus for improved devouring plague.

Patch by dr.tenma.
Fixes issue #2785

--HG--
branch : trunk

src/server/game/Spells/SpellMgr.cpp

@@ -3874,6 +3874,10 @@ void SpellMgr::LoadSpellCustomAttr()
             spellInfo->EffectImplicitTargetA[0] = TARGET_DST_DB;
             count++;
             break;
+        case 63675: // Improved Devouring Plague
+            spellInfo->AttributesEx3 |= SPELL_ATTR_EX3_NO_DONE_BONUS;
+            count++;
+            break;
         default:
             break;
         }