Add indices for `dsaReports` to `INDEXES.md`

[nick-funk]

What does this PR do?

Add missing indices for dsaReports to INDEXES.md

These changes will impact:

• [ ] commenters
• [ ] moderators
• [ ] admins
• [X] developers

What changes to the GraphQL/Database Schema does this PR introduce?

None

Does this PR introduce any new environment variables or feature flags?

No

If any indexes were added, were they added to INDEXES.md?

db.dsaReports.createIndex({ tenantID: 1, id: 1 }, { unique: true });
db.dsaReports.createIndex({ status: 1, createdAt: 1, tenantID: 1 });
db.dsaReports.createIndex({ referenceID: 1, tenantID: 1 });
db.dsaReports.createIndex({ submissionID: 1, tenantID: 1 });

Added to INDEXES.md.

How do I test this PR?

• Use mongo compass to create indices
• Use DSA functionality, see usage of the indices for their specific purposes

Where any tests migrated to React Testing Library?

No

How do we deploy this PR?

• When DSA is deployed to an instance, add these indexes to their appropriate collections.

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