Core/Spells: Effect leap back fix (#18057)

* Fixed unintentional typo?

Seemed to fix the issues related to the effect for the spells I tried.
Sometimes the caster triggers leapback onto targets, and with the old
code, it instead made the caster leap back instead of its targets

(cherry picked from commit 08aab73c7fd0a76caeecc244fc40dbf30cd23e51)

src/server/game/Spells/SpellEffects.cpp

@@ -4492,7 +4492,7 @@ void Spell::EffectLeapBack(SpellEffIndex effIndex)
     float speedxy = m_spellInfo->Effects[effIndex].MiscValue / 10.f;
     float speedz = damage/ 10.f;
     //1891: Disengage
-    m_caster->JumpTo(speedxy, speedz, m_spellInfo->SpellIconID != 1891);
+    unitTarget->JumpTo(speedxy, speedz, m_spellInfo->SpellIconID != 1891);
 }
 
 void Spell::EffectQuestClear(SpellEffIndex effIndex)