MM-44638: Remove upgrade.go (#20309)

We remove any remaining migrations from the upgrade.go file

```release-note
NONE
```

db/migrations/postgres/000088_remaining_migrations.down.sql

@@ -0,0 +1 @@
+-- Skipping it because the forward migrations are destructive

db/migrations/postgres/000088_remaining_migrations.up.sql

@@ -0,0 +1,27 @@
+DROP TABLE IF EXISTS jobstatuses;
+
+DROP TABLE IF EXISTS passwordrecovery;
+
+DO $$
+<<migrate_theme>>
+DECLARE
+    col_exist boolean := false;
+BEGIN
+    SELECT count(*) != 0 INTO col_exist
+    FROM information_schema.columns
+    WHERE table_name = 'users'
+    AND column_name = 'themeprops';
+
+    IF col_exist THEN
+		INSERT INTO
+			preferences(userid, category, name, value)
+		SELECT
+			id, '', '', themeprops
+		FROM
+			users
+		WHERE
+			users.themeprops != 'null';
+
+        ALTER TABLE users DROP COLUMN themeprops;
+    END IF;
+END migrate_theme $$;