Improve IcebergCommitExec to correctly specify properties schema (#22)

Author: sgrebnov

crates/integrations/datafusion/src/physical_plan/commit.rs

@@ -57,14 +57,17 @@ impl IcebergCommitExec {
         input: Arc<dyn ExecutionPlan>,
         schema: ArrowSchemaRef,
     ) -> Self {
-        let plan_properties = Self::compute_properties(schema.clone());
+
+        let count_schema = Self::make_count_schema();
+
+        let plan_properties = Self::compute_properties(Arc::clone(&count_schema));
 
         Self {
             table,
             catalog,
             input,
             schema,
-            count_schema: Self::make_count_schema(),
+            count_schema,
             plan_properties,
         }
     }