Clarify when migration tests are necessary (#14023)

Author: wedamija

develop-docs/backend/application-domains/database-migrations/index.mdx

@@ -76,8 +76,9 @@ There are some things we need to be careful about when running migrations.
 
 ### Testing
 
-Database migrations are risky operations that can lead to irreversible data loss or corruption. This is especially true for [data migrations](https://docs.djangoproject.com/en/4.0/topics/migrations/#data-migrations).
-For this reason, every migration should have a corresponding integration test.
+Note: Regular migrations that modify table structure don't need migration tests
+
+[Data migrations](https://docs.djangoproject.com/en/4.0/topics/migrations/#data-migrations) are particularly risky, since they operate on data and can lead to irreversible data loss or corruption. For this reason, every data migration should have a corresponding integration test.
 
 To test your migration, derive a test case from `TestMigrations` and add it to `tests/sentry/migrations`.
 For example: