Fix Luacheck

Author: Snakybo

.luacheckrc

@@ -157,6 +157,7 @@ read_globals = {
 	"IsModifierKeyDown",
 	"IsMouseButtonDown",
 	"IsPassiveSpell",
+	"issecretvalue",
 	"IsShiftKeyDown",
 	"IsSpellKnown",
 	"IsSpellKnownOrOverridesKnown",
@@ -218,6 +219,7 @@ read_globals = {
 	"UnitGUID",
 	"UnitIsDeadOrGhost",
 	"UnitIsFriend",
+	"UnitIsUnit",
 	"UnitIsVisible",
 	"UnitLevel",
 	"UnitName",