Enable Sortable for lowstock grid

[JustinElst]

Enable Sortable for lowstock grid

Description (*)

Enable Sortable for lowstock grid, i don't see a reason why it was disabled in the first place.

Manual testing scenarios (*)

1. Open a magento Admin interface
2. Goto Reports -> Products -> Low Stock
3. Click on one of the headers (SKU for example) it will not sort

Contribution checklist (*)

• [x] Pull request has a meaningful description of its purpose
• [x] All commits are accompanied by meaningful commit messages
• [x] All new or changed code is covered with unit/integration tests (if applicable)
• [x] All automated tests passed successfully (all builds are green)