fix: resolve PR comments

Author: MichaelScofield

src/datanode/src/instance/sql.rs

@@ -138,13 +138,11 @@ impl Instance {
                 unimplemented!("SHOW CREATE TABLE is unimplemented yet");
             }
             QueryStatement::Sql(Statement::Use(schema)) => {
-                let catalog = query_ctx
-                    .current_catalog()
-                    .as_deref()
-                    .unwrap_or(DEFAULT_CATALOG_NAME);
+                let catalog = query_ctx.current_catalog();
+                let catalog = catalog.as_deref().unwrap_or(DEFAULT_CATALOG_NAME);
 
                 ensure!(
-                    self.is_valid_schema(&catalog, &schema)?,
+                    self.is_valid_schema(catalog, &schema)?,
                     error::DatabaseNotFoundSnafu { catalog, schema }
                 );