Point migration test at auto_join migration 0079

The merge renumbered the auto_join migration to 0079, but the
consolidated-schema test still read it from index 75.

Co-authored-by: Elrond <28d6302a099e5225b02c4155ac4236e4912603df2ab08dbfc2f4fef08ce598c8@buzz.block.builderlab.xyz>
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: tornquist <tornquist@squareup.com>

crates/buzz-db/src/runtime/migration.rs

@@ -780,7 +780,7 @@ mod postgres_tests {
         for (index, migration) in migrations.iter().enumerate() {
             assert_eq!(migration.version, (index + 1) as i64);
         }
-        assert!(migrations[75]
+        assert!(migrations[78]
             .sql
             .as_str()
             .contains("ADD COLUMN auto_join BOOLEAN NOT NULL DEFAULT false"));