Bugfixing of `Assign Website at the time of Creation to the Default Stock`

Bugfixing of `Assign Website at the time of Creation to the Default Stock`
PR: https://github.com/magento-engcom/msi/pull/165

Need do fix \Magento\InventorySales\Test\Integration\AssignWebsiteToDefaultStockTest on Travis
Looks likes we need to one more observer (remove sales channels links after website deleting)
For details see https://travis-ci.org/magento-engcom/msi/jobs/298494303