[BUGFIX]: argilla server: install default psycopy2 driver used by a…

…lembic (#5672)

# Description
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dependencies that are required for this change. -->

Alembic will use psycopy2 driver by default. We still need to install it
to avoid startup errors.

**Type of change**
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PR according to the type of change -->

- Bug fix (non-breaking change which fixes an issue)

**How Has This Been Tested**
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**Checklist**
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- I added relevant documentation
- I followed the style guidelines of this project
- I did a self-review of my code
- I made corresponding changes to the documentation
- I confirm My changes generate no new warnings
- I have added tests that prove my fix is effective or that my feature
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argilla-server/pyproject.toml

@@ -63,7 +63,7 @@ dependencies = [
 
 [project.optional-dependencies]
 postgresql = [
-    "psycopg ~= 3.2.0",
+    "psycopg2 ~= 2.9.0",
     # Async PostgreSQL
     "asyncpg ~= 0.30.0",
 ]