catalog: Remove deploy gen req from savepoint

Previously, the catalog required a deploy generation when opening in
savepoint mode. However, the upgrade checker has no access to a deploy
generation and was failing to open a savepoint catalog. Ideally, the
upgrade checker would have a deploy generation so that it can test the
exact code path that an upgrade would take. For now, we're removing the
requirement to unblock the upgrade checker.

src/catalog/src/durable/persist.rs

@@ -1240,7 +1240,7 @@ impl UnopenedPersistCatalogState {
                 .into());
             }
             (
-                Mode::Writable | Mode::Savepoint,
+                Mode::Writable,
                 FenceableToken::Initializing {
                     current_deploy_generation: None,
                     ..