[12.x] Fix mistake in asJson call in HasAttributes.php that was recently introduced

[AndrewMast]

PR #54992 introduced a new json:unicode cast.

However, an issue was introduced. In HasAttributes.php, in one call to the updated asJson method, hasCast() is being called instead of getJsonCastFlags().

Changes

Old

$value = $this->asJson($this->getArrayAttributeWithValue(
    $path, $key, $value
), $this->hasCast($key, ['json:unicode']));

New

$value = $this->asJson($this->getArrayAttributeWithValue(
    $path, $key, $value
), $this->getJsonCastFlags($key));