Drop trending_projects table

What does this MR do and why?

Drops the trending_projects table and removes the TrendingProject ActiveRecord model.

This is step 3 of removing TrendingProjectsWorker. The trending projects feature was retired in 19.0 and the worker no-oped in 19.1. With no readers or writers left, the table can be dropped safely.

References

• Step 3 issue: #555343 (closed)
• Context: #553408 (closed)
• Prerequisite (step 2, merged): #601483 (closed)

Data Deletion Impact

Data Recovery

In the event of an incident, the trending_projects table can be recovered from the migration's down method. The table can be repopulated by simply running TrendingProject.refresh!.

Records Affected

The trending_projects table typically contains a small number of records (up to 100 projects based on the PROJECTS_LIMIT constant in the model). The exact number varies based on the activity in the system, but this is a minimal dataset.

User Experience Impact

No user-facing impact. The trending projects feature was already retired in version 19.0 and the worker was no-oped in 19.1. This table has had no readers or writers for multiple releases, so its removal will not affect any user-visible functionality or features.

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