fix: change object cache retrieval method visibility

Co-authored-by: Renjie Liu <[email protected]>

Author: sdd

crates/iceberg/src/table.rs

@@ -191,7 +191,7 @@ impl Table {
     }
 
     /// Returns this table's object cache
-    pub fn object_cache(&self) -> Arc<ObjectCache> {
+    pub(crate) fn object_cache(&self) -> Arc<ObjectCache> {
         self.object_cache.clone()
     }