Add test for nested array dim fetch with by-ref parameter

Address review comment: test that `$array[1][]` passed to a
by-reference parameter also does not produce a false positive.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

tests/PHPStan/Rules/Arrays/data/bug-5290.php

@@ -22,3 +22,6 @@ public function bar(?bool &$value): void {
 
 $foo = new Foo();
 $foo->bar($array[]);
+
+// Nested array dim fetch with by-ref parameter
+set($array[1][]);