WIP: Drop UUID column on vulnerability_occurrences

What does this MR do?

As per #212322 (closed) the uuid column is unused and should be dropped. This is the second MR as outlined in #212322 (comment 366879511)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.