Core/Auras: fixed off by one error in counting SPELL_ATTR5_START_PERIODIC_AT_APPLY ticks

- Made SpellInfo::GetMaxTicks and AuraEffect::GetTotalTicks return the same number without mods (dumped arbitrary default return value of 6 and arbitrary 30 sec limit)
- They should be streamlined whenever SPELL_AURA_48 is implemented

(cherry picked from commit 7dff0e3246f68c39e122e6ccb93b18c29f6df130)

src/server/scripts/Spells/spell_priest.cpp

@@ -878,6 +878,8 @@ class spell_pri_t10_heal_2p_bonus : public SpellScriptLoader
 
                 SpellInfo const* spellInfo = sSpellMgr->AssertSpellInfo(SPELL_PRIEST_BLESSED_HEALING, GetCastDifficulty());
                 int32 amount = CalculatePct(static_cast<int32>(healInfo->GetHeal()), aurEff->GetAmount());
+
+                ASSERT(spellInfo->GetMaxTicks() > 0);
                 amount /= spellInfo->GetMaxTicks();
 
                 // Add remaining ticks to healing done