Fix StateEnum.toArray() to exercise recursion path and clean up test comments

[Copilot]

The original StateEnum::toArray() returned scalar strings, so the test never exercised the actual recursion path reported in the issue — where normalizeValue() calling toArray() on an enum yields more enum objects (which also have toArray()), risking infinite recursion.

Changes

• tests/_support/Enum/StateEnum.php: Changed toArray() to return self::cases() (array of UnitEnum objects) instead of scalar strings via array_column. This ensures the test genuinely covers the recursive scenario.
• tests/system/Entity/EntityTest.php: Removed verbose inline comments from testInjectRawDataWithEnumThatHasToArrayMethod(); replaced with a @see docblock pointing to the issue.

// Before — returns scalars, doesn't test recursion
public function toArray(): array
{
    return array_column(self::cases(), 'value');
}

// After — returns UnitEnum objects, testing that normalizeValue()
// takes the UnitEnum branch instead of calling toArray() recursively
public function toArray(): array
{
    return self::cases();
}