[REV] Revert "[FIX] modules: load demo data fallback"
[REV] Revert "[FIX] modules: load demo data fallback"

This reverts commit 5f4a9451828fff1919c74e421001bc111c5c138d.
The cure is worse than the original disease.

The main installation cursor often holds exclusive locks (due to DDL
changes) on vital tables such as res_users. As a result, using
another cursor to perform changes while the main cursor is waiting
is extremely deadlock-prone. And these deadlocks can't be detected by
PostgreSQL as they mix Python-SQL locking, which leads to deadlocked
HTTP workers.

Related to:
- opw-1916918
- #29528

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