fix: Fixes double calls with Target cancel and spell sequences (#1840)

### Summary
- Cleans up target cancellation being called incorrectly.
- An invalid target type (which should never happen), now calls `OnTargetUntargetable` instead of `OnTargetCanceled`
- Removes double calls to `FinishSequence` in Spells.

Projects/UOContent/Spells/Necromancy/PainSpike.cs

@@ -81,8 +81,6 @@ public class PainSpikeSpell : NecromancerSpell, ISpellTargetingMobile
             // SpellHelper.Damage( this, m, damage, 100, 0, 0, 0, 0, Misc.DFAlgorithm.PainSpike );
             HarmfulSpell(m);
         }
-
-        FinishSequence();
     }
 
     public override void OnCast()
@@ -114,4 +112,4 @@ public class PainSpikeSpell : NecromancerSpell, ISpellTargetingMobile
             BuffInfo.RemoveBuff(_mobile, BuffIcon.PainSpike);
         }
     }
-}
+}