Fix always-true detection in in_array with union type haystack

Author: sayuprc

src/Rules/Comparison/ImpossibleCheckTypeHelper.php

@@ -153,6 +153,10 @@ public function findSpecifiedType(
 							foreach ($haystackArrayTypes as $haystackArrayType) {
 								if ($haystackArrayType instanceof ConstantArrayType) {
 									foreach ($haystackArrayType->getValueTypes() as $i => $haystackArrayValueType) {
+										if ($haystackArrayValueType instanceof UnionType) {
+											continue;
+										}
+
 										if ($haystackArrayType->isOptionalKey($i)) {
 											continue;
 										}