Fix psalm errors (#376)

Author: vjik

src/Schema.php

@@ -250,6 +250,7 @@ protected function loadTableIndexes(string $tableName): array
             ':tableName' => $nameParts['name'],
         ])->queryAll();
 
+        /** @psalm-var list<array<string,mixed>> $indexes */
         $indexes = array_map(array_change_key_case(...), $indexes);
         $indexes = DbArrayHelper::arrange($indexes, ['name']);
 
@@ -493,6 +494,7 @@ private function loadTableConstraints(string $tableName, string $returnType): ar
             ':tableName' => $nameParts['name'],
         ])->queryAll();
 
+        /** @psalm-var list<array<string,mixed>> $constraints */
         $constraints = array_map(array_change_key_case(...), $constraints);
         $constraints = DbArrayHelper::arrange($constraints, ['type', 'name']);